kbuild: cherry-pick kbuild changes from Linux

b42841b7bb62 kbuild: Get rid of KBUILD_STR
2aedcd098a94 kbuild: suppress annoying "... is up to date." message
9c8fa9bc08f6 kbuild: fix if_change and friends to consider argument order
ebf003f0cfb3 kbuild: Consolidate header generation from ASM offset information
2982c953570b kbuild: remove redundant $(wildcard ...) for cmd_files calculation
8a78756eb545 kbuild: create object directories simpler and faster
4d4b5c2e3b6e treewide: remove explicit rules for *offsets.s
01d509a48b46 kbuild: remove unimportant comments from ./Kbuild

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
diff --git a/Kbuild b/Kbuild
index e2e3b29..6014f7c 100644
--- a/Kbuild
+++ b/Kbuild
@@ -1,54 +1,20 @@
+# SPDX-License-Identifier: GPL-2.0
 #
 # Kbuild for top-level directory of U-Boot
-# This file takes care of the following:
-# 1) Generate generic-asm-offsets.h
-# 2) Generate asm-offsets.h
-
-# Default sed regexp - multiline due to syntax constraints
-define sed-y
-	"s:[[:space:]]*\.ascii[[:space:]]*\"\(.*\)\":\1:; \
-	/^->/{s:->#\(.*\):/* \1 */:; \
-	s:^->\([^ ]*\) [\$$#]*\([-0-9]*\) \(.*\):#define \1 \2 /* \3 */:; \
-	s:^->\([^ ]*\) [\$$#]*\([^ ]*\) \(.*\):#define \1 \2 /* \3 */:; \
-	s:->::; p;}"
-endef
-
-# Use filechk to avoid rebuilds when a header changes, but the resulting file
-# does not
-define filechk_offsets
-	(set -e; \
-	 echo "#ifndef $2"; \
-	 echo "#define $2"; \
-	 echo "/*"; \
-	 echo " * DO NOT MODIFY."; \
-	 echo " *"; \
-	 echo " * This file was generated by Kbuild"; \
-	 echo " */"; \
-	 echo ""; \
-	 sed -ne $(sed-y); \
-	 echo ""; \
-	 echo "#endif" )
-endef
 
 #####
-# 1) Generate generic-asm-offsets.h
+# Generate generic-asm-offsets.h
 
 generic-offsets-file := include/generated/generic-asm-offsets.h
 
 always  := $(generic-offsets-file)
 targets := lib/asm-offsets.s
 
-# We use internal kbuild rules to avoid the "is up to date" message from make
-lib/asm-offsets.s: lib/asm-offsets.c FORCE
-	$(Q)mkdir -p $(dir $@)
-	$(call if_changed_dep,cc_s_c)
-
 $(obj)/$(generic-offsets-file): lib/asm-offsets.s FORCE
 	$(call filechk,offsets,__GENERIC_ASM_OFFSETS_H__)
 
 #####
-# 2) Generate asm-offsets.h
-#
+# Generate asm-offsets.h
 
 ifneq ($(wildcard $(srctree)/arch/$(ARCH)/lib/asm-offsets.c),)
 offsets-file := include/generated/asm-offsets.h
@@ -59,10 +25,5 @@
 
 CFLAGS_asm-offsets.o := -DDO_DEPS_ONLY
 
-# We use internal kbuild rules to avoid the "is up to date" message from make
-arch/$(ARCH)/lib/asm-offsets.s: arch/$(ARCH)/lib/asm-offsets.c FORCE
-	$(Q)mkdir -p $(dir $@)
-	$(call if_changed_dep,cc_s_c)
-
 $(obj)/$(offsets-file): arch/$(ARCH)/lib/asm-offsets.s FORCE
 	$(call filechk,offsets,__ASM_OFFSETS_H__)