Cronet 121.0.6167.71: set hardening mode for boringssl

libc++ started requiring hardening mode for our c++ targets.
https://github.com/llvm/llvm-project/pull/70575
This only started failing since they removed the default
hardening mode.

Chromium switched to HARDENING_MODE_EXTENSIVE in https://crrev.com/c/5014271

Bug: b/322154153
Change-Id: I538654e05ddbee3120e13f7b19df72097b77bb6d
1 file changed