abuild: Avoid race condition when running abuild parallely

abuild: Avoid race condition when running abuild parallely

By moving the just-created file away, parallel runs of abuild might break.

Change-Id: I03368f00e9b11dad4c80d41279970e28debc7ed5
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: http://review.coreboot.org/405
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>