Revert of Silence -Wclobbered in each file that needs it. (patchset #2 id:20001 of...

Revert of Silence -Wclobbered in each file that needs it. (patchset #2 id:20001 of https://codereview.chromium.org/2184823009/ )

Reason for revert:
Jpeg strategy seems to be leading to crashes.  Gonna go back to warning squelch.

Original issue's description:
> Silence -Wclobbered in each file that needs it.
>
> BUG=skia:
> GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2184823009
>
> Committed: https://skia.googlesource.com/skia/+/03f704a343d7a82974f977eda8789a8c721c93e5

TBR=msarett@google.com,mtklein@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review-Url: https://codereview.chromium.org/2188313003