Enable warning -Wformat-nonliteral.

Change-Id: I5147bea5b113d41e1d47fabca51dfbbc961fa70f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/506836
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
1 file changed