switch android builds to libc++

All other options are going away real soon now.

Change-Id: I57051fdabc2b0fd18fd133c9fb345ffa5a46e5db
Reviewed-on: https://skia-review.googlesource.com/92300
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Mike Klein <mtklein@chromium.org>
1 file changed