This is to ease compiling against cryptography.io. (It expects anything which has EVP_DigestSign to also have this function.) Change-Id: I2bb4f4f01770d789e68fe84beed3393b1f004081 Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/35805 Reviewed-by: Adam Langley <agl@google.com>