I added this when we were moving from gcc to clang on OS X many years
ago.  Now that gcc has been deprecated on mac for many years, this
is safe to remove (clang errors on this pattern).

This check took 0.6s during `git cl presubmit` on a recent change of
mine, so it should speed presubmit up a bit.

Bug: none
Change-Id: Ia29b046807582e056115519fb5b34ee8a1b9ff91
Reviewed-on: https://chromium-review.googlesource.com/553238Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>