Remove BIO dependency from cmac_test.

This is the only test amongst the tests for core crypto functionality
that depends on crypto/bio. This change removes that dependency. This
also factors out the duplicative hexdump logic into a shared function.

Change-Id: Ic280a71d086555a6993c05f183b94e1d38b60932
Reviewed-on: https://boringssl-review.googlesource.com/5622
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/crypto/test/CMakeLists.txt b/crypto/test/CMakeLists.txt
index 84a6174..8c75314 100644
--- a/crypto/test/CMakeLists.txt
+++ b/crypto/test/CMakeLists.txt
@@ -5,4 +5,5 @@
 
   file_test.cc
   malloc.cc
+  test_util.cc
 )