Allow overriding the build directly (default: coreboot-builds) using the COREBOOT_BUILD_DIR variable, in addition to setting it through the -o parameter. This helps with build nodes where jenkins wants to run the same command everywhere but allows different environment variables. Change-Id: If907897cf6ac01caa7d1e4b51aad4c005356bc5b Signed-off-by: Patrick Georgi <patrick@georgi-clan.de> Reviewed-on: http://review.coreboot.org/4543 Tested-by: build bot (Jenkins) Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>