home-environment: use explicit PATH in activation

In the activation script we expect to use the tools provided by GNU
Core Utilities and GNU Bash. This commit therefore explicitly add
these first in the `PATH` environment variable.

modules/home-environment.nix

@@ -375,6 +375,11 @@ in
           set -eu
           set -o pipefail
 
+          # This code explicitly requires GNU Core Utilities and Bash.
+          # We therefore need to ensure they are prioritized over any
+          # other similarly named tools on the system.
+          export PATH="${pkgs.coreutils}/bin:${pkgs.bash}/bin:$PATH"
+
           . ${./lib-bash/color-echo.sh}
 
           ${builtins.readFile ./lib-bash/activation-init.sh}