Fix imports in gcc_toolchain.gni to not rely on //tools.

tools/grit/grit_rule.gni

Index: tools/grit/grit_rule.gni
diff --git a/tools/grit/grit_rule.gni b/tools/grit/grit_rule.gni
index d1207ad63e5f0eb641a95686d8681779834d7bb9..4bb8500152c2d07a936992b4e2fd2032406fbf54 100644
--- a/tools/grit/grit_rule.gni
+++ b/tools/grit/grit_rule.gni
@@ -84,12 +84,6 @@ import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//third_party/closure_compiler/closure_args.gni")
 
-declare_args() {
-  # Enables used resource whitelist generation. Set for official builds only
-  # as a large amount of build output is generated.
-  enable_resource_whitelist_generation = is_android && is_official_build
-}
-
 assert(!enable_resource_whitelist_generation || is_android,
        "resource whitelist generation only works on android")