elixir-ls: fix elixir executable in path

(cherry picked from commit b4eee17286)

pkgs/development/beam-modules/elixir-ls/launch.sh.patch

@@ -1,5 +1,5 @@
 diff --git c/scripts/launch.sh w/scripts/launch.sh
-index 21afbb1e..6b61f0b4 100755
+index 21afbb1e..8bc5c382 100755
 --- c/scripts/launch.sh
 +++ w/scripts/launch.sh
 @@ -1,125 +1,4 @@
@@ -129,7 +129,7 @@ index 21afbb1e..6b61f0b4 100755
  
  # In case that people want to tweak the path, which Elixir to use, or
  # whatever prior to launching the language server or the debug adapter, we
-@@ -138,29 +17,18 @@ fi
+@@ -138,29 +17,22 @@ fi
  # script so we can correctly configure the Erlang library path to
  # include the local .ez files, and then do what we were asked to do.
  
@@ -166,4 +166,8 @@ index 21afbb1e..6b61f0b4 100755
 +ELX_STDLIB_PATH=${ELX_STDLIB_PATH:-@elixir@/lib/elixir}
 +export ELX_STDLIB_PATH
 +
++# ensure our elixir is in the path
++PATH="@elixir@/bin:$PATH"
++export PATH
++
 +source "$SCRIPTPATH/exec.bash"