external/boringssl: add -Wno-unused-parameters.

Clang is throwing errors becaues of unused parameters, but not all
parameters are supposed to be used. Also, having errors in Android that
aren't enforced upstream invites this problem repeating ever more in the
future.

Bug: 21304073
Change-Id: I8e81d6d6659896b5b16a1406e8637e489f8059fd
(cherry picked from commit 71cbcbedb24dacc402647b2e8b2a52b76cf5cfc2)
1 file changed