certs: dm-verity: add keyring certification for verity

Enable SYSTEM_TRUSTED_KEYS and add certification
for x509 signing for system.

CRs-Fixed: 1116507
Change-Id: I01298d75da0ff9faee2d01118107d53e9a2aef8a
Signed-off-by: Jeevan Shriram <jshriram@codeaurora.org>
Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org>
diff --git a/certs/Makefile b/certs/Makefile
index 2773c4a..9d89b99 100644
--- a/certs/Makefile
+++ b/certs/Makefile
@@ -17,6 +17,10 @@
 quiet_cmd_extract_certs  = EXTRACT_CERTS   $(patsubst "%",%,$(2))
       cmd_extract_certs  = scripts/extract-cert $(2) $@ || ( rm $@; exit 1)
 
+ifeq ($(CONFIG_SYSTEM_TRUSTED_KEYS),"verity.x509.pem")
+SYSTEM_TRUSTED_KEYS_SRCPREFIX := $(srctree)/certs/
+endif
+
 targets += x509_certificate_list
 $(obj)/x509_certificate_list: scripts/extract-cert $(SYSTEM_TRUSTED_KEYS_SRCPREFIX)$(SYSTEM_TRUSTED_KEYS_FILENAME) FORCE
 	$(call if_changed,extract_certs,$(SYSTEM_TRUSTED_KEYS_SRCPREFIX)$(CONFIG_SYSTEM_TRUSTED_KEYS))