Prior to 3.12 (which we won't be requiring until July), OBJECT libraries cannot be used with target_link_libraries. That means they cannot pick up INTERFACE_INCLUDE_DIRECTORIES, which makes them pretty unusable in the "modern CMake" style. Just switch it to a static library to unbreak the build in CMake 3.10. For some link ordering reason I don't understand, this also requires explicitly linking boringssl_gtest to libcxx when we USE_CUSTOM_LIBCXX is set. Change-Id: Ia9d8351551f5da060248aa3ca73fe04473bf62aa Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/57345 Commit-Queue: Bob Beck <bbe@google.com> Reviewed-by: Bob Beck <bbe@google.com> Auto-Submit: David Benjamin <davidben@google.com>