Revert "GN: detect is_clang, use it to switch Clang to warning blacklist."

This reverts commit I09c3487adfeb26a6fb07e1939cb927c5d7de3107.

Reason for revert: -Wover-aligned on x86 Android bots

Original issue's description:
> GN: detect is_clang, use it to switch Clang to warning blacklist.
> 
> BUG=skia:
> 
> GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2599
> 
> Change-Id: I09c3487adfeb26a6fb07e1939cb927c5d7de3107
> Reviewed-on: https://skia-review.googlesource.com/2599
> Reviewed-by: Ben Wagner <bungeman@google.com>
> Commit-Queue: Mike Klein <mtklein@chromium.org>
> 

TBR=mtklein@chromium.org,bungeman@google.com,reviews@skia.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Change-Id: Ic07bf7896a305be6c377f14a573cb10836f1a6f8
Reviewed-on: https://skia-review.googlesource.com/2601
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
2 files changed