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/stdenv/linux/default.nix

@@ -83,9 +83,9 @@ rec {
           curl = bootstrapTools;
         };
 
-        gcc = if isNull gccPlain
-              then "/no-such-path"
-              else lib.makeOverridable (import ../../build-support/gcc-wrapper) {
+        cc = if isNull gccPlain
+             then "/no-such-path"
+             else lib.makeOverridable (import ../../build-support/gcc-wrapper) {
           nativeTools = false;
           nativeLibc = false;
           gcc = gccPlain;
@@ -232,7 +232,7 @@ rec {
       gcc = lib.makeOverridable (import ../../build-support/gcc-wrapper) {
         nativeTools = false;
         nativeLibc = false;
-        gcc = stage4.stdenv.gcc.gcc;
+        gcc = stage4.stdenv.cc.gcc;
         libc = stage4.pkgs.glibc;
         inherit (stage4.pkgs) binutils coreutils;
         name = "";
@@ -267,9 +267,9 @@ rec {
 
     extraBuildInputs = [ stage4.pkgs.patchelf stage4.pkgs.paxctl ];
 
-    gcc = stage4.pkgs.gcc;
+    cc = stage4.pkgs.gcc;
 
-    shell = gcc.shell;
+    shell = cc.shell;
 
     inherit (stage4.stdenv) fetchurlBoot;
 
@@ -286,7 +286,7 @@ rec {
       ];
 
     overrides = pkgs: {
-      inherit gcc;
+      inherit cc;
       inherit (stage4.pkgs)
         gzip bzip2 xz bash binutils coreutils diffutils findutils gawk
         glibc gnumake gnused gnutar gnugrep gnupatch patchelf