Support macos system to use ghcs-nix
Currently, building ghcs.nix on macos does not work.
% nix build -f . ghc-9_6_1-alpha2
error: cannot coerce null to a string
at /Users/ianwookim/repo/srcc/ghcs-nix/hadrian.nix:151:23:
150| # Unicode locale.
151| LOCALE_ARCHIVE = "${glibcLocales}/lib/locale/locale-archive";
| ^
152| LANG = "C.UTF-8";
(use '--show-trace' to show detailed location information)
Supporting macos will be very benefitable as more developers can easily access multiple versions of GHCs. Thanks!