Simplify logic for a gcc + libc++ build

This CL addresses some ghostly comments from
https://chromium-review.googlesource.com/c/chromium/src/+/772959

R=thakis

Change-Id: I8ce1e1d6a55ec7bfe61a59b27de1bc586abbe55d
Reviewed-on: https://chromium-review.googlesource.com/874810
Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#530212}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: b6fce873b52eac2a2f6d389f37cdf9e074e1ba8b
1 file changed