gcc: Change default of crossStageStatic param to false

This gets us one step closer to removing `gccCrossStageFinal`.

Care is taken to avoid a mass rebuild; will clean up with one later.

pkgs/development/compilers/gcc/6/default.nix

@@ -26,7 +26,7 @@
 , enablePlugin ? true             # whether to support user-supplied plug-ins
 , name ? "gcc"
 , libcCross ? null
-, crossStageStatic ? true
+, crossStageStatic ? false
 , gnat ? null
 , libpthread ? null, libpthreadCross ? null  # required for GNU/Hurd
 , stripped ? true
@@ -292,7 +292,9 @@ stdenv.mkDerivation ({
         ''
     else null;
 
-  inherit noSysDirs staticCompiler langJava crossStageStatic
+  # TODO(@Ericson2314): Make passthru instead. Weird to avoid mass rebuild,
+  crossStageStatic = targetPlatform == hostPlatform || crossStageStatic;
+  inherit noSysDirs staticCompiler langJava
     libcCross crossMingw;
 
   nativeBuildInputs = [ texinfo which gettext ]