add compiler flags to control slugs

Change-Id: I581f78b829a810d93a065cbbda9a1f87c41f5c45
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/475541
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Herb Derby <herb@google.com>
2 files changed