Change occurrences of gcc to the more general cc

This is done for the sake of Yosemite, which does not have gcc, and yet
this change is also compatible with Linux.

pkgs/games/adom/default.nix

@@ -7,7 +7,7 @@ let
 
   inherit (xlibs) libXext libX11;
 
-  lpath = "${stdenv.gcc.gcc}/lib64:" + stdenv.lib.makeSearchPath "lib" [
+  lpath = "${stdenv.cc.gcc}/lib64:" + stdenv.lib.makeSearchPath "lib" [
       zlib libmad libpng12 libcaca libXext libX11 mesa alsaLib pulseaudio];
 
 in
@@ -45,7 +45,7 @@ stdenv.mkDerivation rec {
     done
 
     ${patchelf}/bin/patchelf \
-      --set-interpreter "$(cat $NIX_GCC/nix-support/dynamic-linker)" \
+      --set-interpreter "$(cat $NIX_CC/nix-support/dynamic-linker)" \
       --set-rpath "$out/lib:${lpath}" \
       $out/adom