# - If no file exist it is created
# - If the content differ the new file is used
# - If they are equal no change, and no timestamp update
-# - stdin is piped in from the first prerequisite ($<) so one has
-# to specify a valid file as first prerequisite (often the kbuild file)
define filechk
$(Q)set -e; \
mkdir -p $(dir $@); \