genbuild_h.sh: use the last git commit as timesource if available

Change-Id: I1472265adac9406a86da22839199ec6bbdaa0c69
Signed-off-by: Alexander Couzens <lynxis@fe80.eu>
Reviewed-on: http://review.coreboot.org/8619
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
1 file changed