payloads/external/Linuxboot/Makefile: Guard u-root Makefile

The u-root.mk makefile needs to be guarded, because it introduces a
dependency on the go tooling.

Signed-off-by: Maximilian Brune <maximilian.brune@9elements.com>
Change-Id: Ia89e4e7b9a1f73a7b622eeaa8d6148d99f9b327a
Reviewed-on: https://review.coreboot.org/c/coreboot/+/76714
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Marvin Drees <marvin.drees@9elements.com>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-by: Fred Reitberger <reitbergerfred@gmail.com>
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>

0 files changed, 0 insertions, 0 deletions