u-boot: Make sure targets aren't duplicated

When U-Boot isn't selected as a payload, two of the targets:
$(project_dir): and $(project_dir)/$(TAG-y) evaluated to the same
value, generating a make warning when running a clean.  By adding
additional text to the file that is created, this is avoided.

Gets rid of these warnings:
Makefile.inc:54: warning: overriding commands for target `u-boot'
Makefile.inc:37: warning: ignoring old commands for target `u-boot'

Change-Id: I4b4df753612b674b3ccde2a757338840be92d1f2
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/13767
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

0 files changed, 0 insertions, 0 deletions