When x509.genkey is created, it prints a log:
Generating X.509 key generation config
..., which is not the ordinary Kbuild log style.
Check-in the default config as certs/default_x509.genkey to make it
readable, and copy it to certs/x509.genkey if it is not present.
The log is shown in the Kbuild style.
COPY certs/x509.genkey
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>