kbuild: do not redirect the first prerequisite for filechk

Currently, filechk unconditionally opens the first prerequisite and
redirects it as the stdin of a filechk_* rule.  Hence, every target
using $(call filechk,...) must list something as the first prerequisite
even if it is unneeded.

'< $<' is actually unneeded in most cases.  Each rule can explicitly
adds it if necessary.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

scripts/Kbuild.include

@@ -56,7 +56,7 @@ kecho := $($(quiet)kecho)
 define filechk
 	$(Q)set -e;				\
 	mkdir -p $(dir $@);			\
-	$(filechk_$(1)) < $< > $@.tmp;		\
+	$(filechk_$(1)) > $@.tmp;		\
 	if [ -r $@ ] && cmp -s $@ $@.tmp; then	\
 		rm -f $@.tmp;			\
 	else					\

scripts/Makefile.lib

@@ -415,7 +415,7 @@ define filechk_offsets
 	 echo " * This file was generated by Kbuild"; \
 	 echo " */"; \
 	 echo ""; \
-	 sed -ne $(sed-offsets); \
+	 sed -ne $(sed-offsets) < $<; \
 	 echo ""; \
 	 echo "#endif" )
 endef