build system: improve portability by not relying on extraordinary dd options

Change-Id: Ibc7fe38ae11e9d477f85fdcf760b27abc6013f94
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-on: http://review.coreboot.org/9791
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
1 file changed