These relocations can be emitted for thread-local data. BoringSSL itself
doesn't include any thread-local variables that need linker support, but
ASAN and MSAN may inject these references in order to handle their own
bookkeeping.
Change-Id: I0c6e61d244be84d6bee5ccbf7c4ff4ea0f0b90fd
Reviewed-on: https://boringssl-review.googlesource.com/15147
Reviewed-by: Adam Langley <agl@google.com>