payloads: Add a target to print payload git urls and directories

Being able to fetch this list will allow the jenkins builder to securely
fetch the external payloads so we can start testing payload builds.

Change-Id: I777229216b2f11f0f427cd5f8cfa003da4171a77
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/14132
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

payloads/external/Memtest86Plus/Makefile

@@ -39,4 +39,7 @@ clean:
 distclean:
 	rm -rf $(project_dir)
 
-.PHONY: all build fetch clean distclean
+print-repo-info:
+	echo "$(project_git_repo) $(project_dir)"
+
+.PHONY: all build fetch clean distclean print-repo-info