Currently only x86 requires special handling here, for simplicity
avoid introducing <arch/rules.h> and deal with this directly in
<rules.h>.
For consistency prefixes are changed from ARCH_ to ENV_.
Change-Id: I95a56dbad3482202f6cc03043589bebfb13c39af
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/35014
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>