build system: prevent race on more tool binaries

ifdfake is the newest tool addition that leads to build time
races on highly parallel builds.

Change-Id: I86289e50079da851dcc8e1c05c2536d5c03de87c
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: http://review.coreboot.org/6197
Tested-by: build bot (Jenkins)
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>