util/abuild: Run `make .xcompile` only once

If abuild called itself recursively, the file already exists and we can
spare us one evaluation of all the makefiles per recursive abuild run.

Change-Id: Id3e2239354ec251c24c03c971987586deeb026c5
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/42640
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Reviewed-by: Reka Norman <rekanorman@chromium.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

0 files changed, 0 insertions, 0 deletions