chromium: make gcc8 build available via buildWithGcc flag

pkgs/applications/networking/browsers/chromium/common.nix

@@ -31,12 +31,13 @@
 , upstream-info
 }:
 
+assert stdenv.cc.isClang -> (stdenv == llvmPackages.stdenv);
+
 buildFun:
 
 with stdenv.lib;
 
 # see http://www.linuxfromscratch.org/blfs/view/cvs/xsoft/chromium.html
-
 let
   # The additional attributes for creating derivations based on the chromium
   # source tree.

pkgs/applications/networking/browsers/chromium/default.nix

@@ -1,5 +1,6 @@
-{ newScope, stdenv, llvmPackages, makeWrapper, makeDesktopItem, ed
+{ newScope, makeWrapper, makeDesktopItem, ed
 , glib, gtk3, gnome3, gsettings-desktop-schemas
+, stdenv, llvmPackages_7, gcc8Stdenv
 
 # package customization
 , channel ? "stable"
@@ -9,17 +10,16 @@
 , proprietaryCodecs ? true
 , enablePepperFlash ? false
 , enableWideVine ? false
+, buildWithGcc ? false
 , cupsSupport ? true
 , pulseSupport ? false
 , commandLineArgs ? ""
 }:
 
-assert stdenv.cc.isClang -> (stdenv == llvmPackages.stdenv);
 let
   callPackage = newScope chromium;
 
   chromium = {
-    inherit stdenv llvmPackages;
 
     upstream-info = (callPackage ./update.nix {}).getChannel channel;
 
@@ -34,7 +34,12 @@ let
     plugins = callPackage ./plugins.nix {
       inherit enablePepperFlash enableWideVine;
     };
-  };
+  } // (if buildWithGcc then {
+          stdenv = gcc8Stdenv;
+        } else {
+          llvmPackages = llvmPackages_7;
+          stdenv = llvmPackages_7.stdenv;
+        });
 
   desktopItem = makeDesktopItem {
     name = "chromium-browser";

pkgs/top-level/all-packages.nix

@@ -16021,14 +16021,8 @@ with pkgs;
     pulseSupport = config.pulseaudio or true;
     enablePepperFlash = config.chromium.enablePepperFlash or false;
     enableWideVine = config.chromium.enableWideVine or false;
-    gnome = gnome2;
-  } // (if stdenv.isAarch64 then {
-          stdenv = gcc8Stdenv;
-        } else {
-          llvmPackages = llvmPackages_7;
-          stdenv = llvmPackages_7.stdenv;
-        })
-   );
+    buildWithGcc = config.chromium.buildWithGcc or stdenv.isAarch64;
+  });
 
   chronos = callPackage ../applications/networking/cluster/chronos { };