CMake targets are visible globally but gtest_main has boringssl-specific
behavior that isn't appropriate for general use.
This change makes it possible to use boringssl and abseil-cpp in the
same project (since abseil-cpp expects gtest_main to exist and be useful
for its own tests).
Change-Id: Icc81c11b8bb4b1e21cea7c9fa725b6c082bd5369
Reviewed-on: https://boringssl-review.googlesource.com/24604
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: Adam Langley <agl@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>