Clean symbol export on mod mock

Merge from Widevine repo of http://go/wvgerrit/42281

This cleans up some of the oemcrypto mock code.  This code is only
used for testing.

bug: 72831885
bug: 69271232
Change-Id: I8add162839d6febe56a89df84e8ae0cf0b97a2d9

libwvdrmengine/oemcrypto/mock/src/oemcrypto_rsa_key_shared.h

@@ -32,6 +32,9 @@ class RSA_shared_ptr {
   bool key_owned_;
 };
 
+// Log errors from BoringSSL.
+void dump_boringssl_error();
+
 }  // namespace wvoec_mock
 
 #endif  // OEMCRYPTO_RSA_KEY_SHARED_H_