Keymaster: add certificate_utils.cpp to build rules.

Bug: None
Change-Id: I6bec6c2857ee9ed450ff32350dfe8999875beb9f
diff --git a/rules.mk b/rules.mk
index 1cb2898..d48a043 100644
--- a/rules.mk
+++ b/rules.mk
@@ -55,6 +55,7 @@
 	$(KEYMASTER_ROOT)/km_openssl/attestation_record.cpp \
 	$(KEYMASTER_ROOT)/km_openssl/attestation_utils.cpp \
 	$(KEYMASTER_ROOT)/km_openssl/block_cipher_operation.cpp \
+	$(KEYMASTER_ROOT)/km_openssl/certificate_utils.cpp \
 	$(KEYMASTER_ROOT)/km_openssl/ckdf.cpp \
 	$(KEYMASTER_ROOT)/km_openssl/ec_key.cpp \
 	$(KEYMASTER_ROOT)/km_openssl/ec_key_factory.cpp \