When building on Mac you see lots of spam about object files with no symbols when linking libskia.a. This filters them out.
We have to do this in a Python script anyway, so I've consolidated into the existing gn/ar.py.
BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4447
Change-Id: I9b18051ba687ec1fcf464a87a8a5929d29c70f24
Reviewed-on: https://skia-review.googlesource.com/4447
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>