Add entry point stubs of each stage for Rex. More functionalities will
be added later.
BUG=b:224325352
TEST=util/abuild/abuild -p none -t google/rex -a -c max
Signed-off-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>
Change-Id: I2310e58ab92bdb0ce86a9f7284cc0b3e04a2889f
Reviewed-on: https://review.coreboot.org/c/coreboot/+/64591
Reviewed-by: Tarun Tuli <taruntuli@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>