Otherwise attempt to build ghcHEAD from local checkout fails as:
$ nix build -L --impure --expr 'with import ~/nm {}; haskell.compiler.ghcHEAD.overrideAttrs (oa: { src = ./.; patches = []; nativeBuildInputs = oa.nativeBuildInputs ++ [ git ]; })' --keep-failed
...
ghc> checking C++ standard library flavour... ./configure: line 11487: /nix/store/r7r10qvsqlnvbzjkjinvscjlahqbxifl-gcc-wrapper-11.3.0/bin/cxx: No such file or directory
I think 'cxx' is not provided by stdenv.
849d47a928