Add basic BLAKE2b-256 support.

Our use-case for this does not require optimisation at the current time,
so a clean C implementation is fine.

Change-Id: I8f29572c33e8dbcc37961c099c71c14aafc8d0a3
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/45164
Reviewed-by: David Benjamin <davidben@google.com>
diff --git a/sources.cmake b/sources.cmake
index d7b527b..9ac55d5 100644
--- a/sources.cmake
+++ b/sources.cmake
@@ -6,6 +6,7 @@
 set(
   CRYPTO_TEST_DATA
 
+  crypto/blake2/blake2b256_tests.txt
   crypto/cipher_extra/test/aes_128_cbc_sha1_tls_implicit_iv_tests.txt
   crypto/cipher_extra/test/aes_128_cbc_sha1_tls_tests.txt
   crypto/cipher_extra/test/aes_128_cbc_sha256_tls_tests.txt