Add comments explaining use of "-Wno-over-aligned"

Follow up to I04a5b013dd0ec8f162046388e89cf08cb9476bab

Change-Id: I5ab77564fe867ad1fef48fb322ff75869c025776
Reviewed-on: https://skia-review.googlesource.com/79040
Commit-Queue: Leon Scroggins <scroggo@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
Reviewed-by: Mike Klein <mtklein@chromium.org>
1 file changed