Fixes necessary to enable in-tree libc++ on Android

All that should be necessary after this change is to flip use_custom_libcxx to
true on Android.

BUG=846855
R=thakis

Change-Id: I386176970ea7f05a9dbd7f04a2254c3a14d5419b
Reviewed-on: https://chromium-review.googlesource.com/c/1377501
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616799}
2 files changed