libpayload: .xcompile target is an actual file

Marking .xcompile as PHONY implies triggering the xcompile script each time make
is invoked. This is particularly problematic, especially when the script cannot
find the crossgcc toolchains on its own and has to be fed XGCCPATH.

Change-Id: Icb5ae82b210bca1ee9cf56d76130eefde481f81e
Signed-off-by: Paul Kocialkowski <contact@paulk.fr>
Reviewed-on: http://review.coreboot.org/11118
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
1 file changed