treewide: refactor .attrs.sh detection

When specifying the `builder` attribute in `stdenv.mkDerivation`, this
will be effectively transformed into

    builtins.derivation {
      builder = stdenv.shell;
      args = [ "-e" builder ];
    }

This also means that `default-builder.sh` is never sourced and as a
result it's not guaranteed that `$NIX_ATTRS_SH_FILE` is set to a correct
location[1].

Also, we need to source `.attrs.sh` to source `$stdenv`. So, the
following is done now:

* If `$NIX_ATTRS_SH_FILE` points to a correct location, then use it.
  Directly using `.attrs.sh` is problematic for `nix-shell(1)` usage
  (see previous commit for more context), so prefer the environment
  variable if possible.

* Otherwise, if `.attrs.sh` exists, then use it. See [1] for when this
  can happen.

* If neither applies, it can be assumed that `__structuredAttrs` is
  turned off and thus nothing needs to be done.

[1] It's possible that it doesn't exist at all - in case of Nix 2.3 or
    it can point to a wrong location on older Nix versions with a bug in
    `__structuredAttrs`.

nixos/modules/services/networking/ircd-hybrid/builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 
 doSub() {

nixos/modules/services/web-servers/jboss/builder.sh

@@ -1,6 +1,6 @@
 set -e
 
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 
 mkdir -p $out/bin

pkgs/applications/misc/adobe-reader/builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 
 echo "unpacking $src..."

pkgs/build-support/fetchbzr/builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source "$stdenv/setup"
 
 echo "exporting \`$url' (revision $rev) into \`$out'"

pkgs/build-support/fetchcvs/builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 
 (echo "#!$SHELL"; \

pkgs/build-support/fetchdarcs/builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 
 tagtext=""

pkgs/build-support/fetchdocker/fetchdocker-builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source "${stdenv}/setup"
 echo "exporting ${repository}/${imageName} (tag: ${tag}) into ${out}"
 mkdir -p "${out}"

pkgs/build-support/fetchfossil/builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 echo "Cloning Fossil $url [$rev] into $out"
 

pkgs/build-support/fetchgit/builder.sh

@@ -3,7 +3,7 @@
 # - revision specified and remote has a HEAD
 # - revision specified and remote without HEAD
 #
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 
 echo "exporting $url (rev $rev) into $out"

pkgs/build-support/fetchhg/builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 echo "getting $url${rev:+ ($rev)} into $out"
 

pkgs/build-support/fetchipfs/builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 
 # Curl flags to handle redirects, not use EPSV, handle cookies for

pkgs/build-support/fetchmtn/builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 
 set -x

pkgs/build-support/fetchsvn/builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 
 echo "exporting $url (r$rev) into $out"

pkgs/build-support/fetchsvnssh/builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 
 echo "exporting $url (r$rev) into $out"

pkgs/build-support/fetchurl/builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 
 source $mirrorsFile

pkgs/desktops/gnustep/make/builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 
 providedPreConfigure="$preConfigure";

pkgs/development/compilers/aspectj/builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 
 export JAVA_HOME=$jre

pkgs/development/compilers/chicken/4/fetchegg/builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 
 echo "exporting egg ${eggName} (version $version) into $out"

pkgs/development/compilers/fpc/binary-builder-darwin.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 
 pkgdir=$(pwd)/pkg

pkgs/development/compilers/fpc/binary-builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 
 tar xf $src

pkgs/development/compilers/ios-cross-compile/9.2_builder.sh

@@ -1,5 +1,5 @@
 # -*- shell-script -*-
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 
 function extract

pkgs/development/compilers/ocaml/builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 
 configureFlags="-prefix $out $configureFlags"

pkgs/development/libraries/glibc/locales-builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 # Glibc cannot have itself in its RPATH.
 export NIX_NO_SELF_RPATH=1
 

pkgs/development/libraries/gtk-sharp/builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 
 genericBuild

pkgs/development/libraries/wtk/builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 
 mkdir unzipped

pkgs/development/perl-modules/generic/builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 
 PERL5LIB="$PERL5LIB${PERL5LIB:+:}$out/lib/perl5/site_perl"

pkgs/development/tools/build-managers/boot/builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 
 boot_bin=$out/bin/boot

pkgs/development/tools/misc/automake/builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 
 # Wrap the given `aclocal' program, appending extra `-I' flags

pkgs/development/tools/parsing/antlr/builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 
 tar zxvf $src

pkgs/misc/cups/drivers/samsung/4.00.39/builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 
 arch=$(uname -m)

pkgs/os-specific/linux/nvidia-x11/builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 
 unpackManually() {

pkgs/os-specific/linux/opengl/xorg-sys/builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 
 mkdir -p $out/lib

pkgs/servers/http/tomcat/axis2/builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 source $stdenv/setup
 
 unzip $src

pkgs/servers/x11/xorg/builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 # This is the builder for all X.org components.
 source $stdenv/setup
 

pkgs/stdenv/generic/default-builder.sh

@@ -1,6 +1,4 @@
-if [ -f .attrs.sh ]; then
-    . .attrs.sh
-fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 
 source $stdenv/setup
 genericBuild

pkgs/test/simple/builder.sh

@@ -1,4 +1,4 @@
-if [ -e .attrs.sh ]; then source .attrs.sh; fi
+if [ -e "$NIX_ATTRS_SH_FILE" ]; then . "$NIX_ATTRS_SH_FILE"; elif [ -f .attrs.sh ]; then . .attrs.sh; fi
 set -x
 
 export NIX_DEBUG=1