Merge pull request #220436 from viraptor/fac-build-fix

fac-build: fix tests calling out to git

pkgs/development/tools/build-managers/fac/default.nix

···
     substituteInPlace src/git.rs \
         --replace 'std::process::Command::new("git")' \
         'std::process::Command::new("${git}/bin/git")'
+    substituteInPlace tests/lib.rs \
+        --replace 'std::process::Command::new("git")' \
+        'std::process::Command::new("${git}/bin/git")'
   '';
 
   meta = with lib; {