Enable printf warnings on SkSL::String.

Change-Id: Ifea2b490b86e69b871d31dea544407e857dc4677
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/371484
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
3 files changed