kbuild: cherry-pick kbuild changes from Linux

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>