disable object-size santizer in debug builds

This avoids a warning-as-error:

 clang-5.0: error: the object size sanitizer has no effect at -O0, but
 is explicitly enabled:

Change-Id: I53a16acc3e743b42fe9c2f35919d3c09d5d601b7
Reviewed-on: https://skia-review.googlesource.com/55720
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Mike Klein <mtklein@chromium.org>
1 file changed