external/boringssl: Sync to 4ca15d5dcbe6e8051a4654df7c971ea8307abfe0.

This includes the following changes:

https://boringssl.googlesource.com/boringssl/+log/56b6c714c9cae5963681ed9dd9f6cabf294e3f80..4ca15d5dcbe6e8051a4654df7c971ea8307abfe0

Test: Treehugger only - this is a trivial change from a single commit
      that shouldn't affect Android at all, it only affects
      boringssl's own builds.
Change-Id: I2427fdca35ae3cb61298c1d0102b9bf191d0d068
4 files changed