Merge tag 'kbuild-v4.15' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild updates from Masahiro Yamada:
 "One of the most remarkable improvements in this cycle is, Kbuild is
  now able to cache the result of shell commands. Some variables are
  expensive to compute, for example, $(call cc-option,...) invokes the
  compiler. It is not efficient to redo this computation every time,
  even when we are not actually building anything. Kbuild creates a
  hidden file ".cache.mk" that contains invoked shell commands and their
  results. The speed-up should be noticeable.

  Summary:

   - Fix arch build issues (hexagon, sh)

   - Clean up various Makefiles and scripts

   - Fix wrong usage of {CFLAGS,LDFLAGS}_MODULE in arch Makefiles

   - Cache variables that are expensive to compute

   - Improve cc-ldopton and ld-option for Clang

   - Optimize output directory creation"

* tag 'kbuild-v4.15' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (30 commits)
  kbuild: move coccicheck help from scripts/Makefile.help to top Makefile
  sh: decompressor: add shipped files to .gitignore
  frv: .gitignore: ignore vmlinux.lds
  selinux: remove unnecessary assignment to subdir-
  kbuild: specify FORCE in Makefile.headersinst as .PHONY target
  kbuild: remove redundant mkdir from ./Kbuild
  kbuild: optimize object directory creation for incremental build
  kbuild: create object directories simpler and faster
  kbuild: filter-out PHONY targets from "targets"
  kbuild: remove redundant $(wildcard ...) for cmd_files calculation
  kbuild: create directory for make cache only when necessary
  sh: select KBUILD_DEFCONFIG depending on ARCH
  kbuild: fix linker feature test macros when cross compiling with Clang
  kbuild: shrink .cache.mk when it exceeds 1000 lines
  kbuild: do not call cc-option before KBUILD_CFLAGS initialization
  kbuild: Cache a few more calls to the compiler
  kbuild: Add a cache for generated variables
  kbuild: add forward declaration of default target to Makefile.asm-generic
  kbuild: remove KBUILD_SUBDIR_ASFLAGS and KBUILD_SUBDIR_CCFLAGS
  hexagon/kbuild: replace CFLAGS_MODULE with KBUILD_CFLAGS_MODULE
  ...

scripts/Makefile.headersinst

@@ -27,11 +27,11 @@ subdirs       := $(patsubst $(srcdir)/%/,%,\
 # Recursion
 __headers: $(subdirs)
 
-.PHONY: $(subdirs)
+PHONY += $(subdirs)
 $(subdirs):
 	$(Q)$(MAKE) $(hdr-inst)=$(obj)/$@ dst=$(dst)/$@
 
-# Skip header install/check for include/uapi and arch/$(hdr-arch)/include/uapi.
+# Skip header install/check for include/uapi and arch/$(SRCARCH)/include/uapi.
 # We have only sub-directories there.
 skip-inst := $(if $(filter %/uapi,$(obj)),1)
 
@@ -115,9 +115,8 @@ $(check-file): scripts/headers_check.pl $(output-files) FORCE
 
 endif
 
-targets := $(wildcard $(sort $(targets)))
 cmd_files := $(wildcard \
-             $(foreach f,$(targets),$(dir $(f)).$(notdir $(f)).cmd))
+             $(foreach f,$(sort $(targets)),$(dir $(f)).$(notdir $(f)).cmd))
 
 ifneq ($(cmd_files),)
 	include $(cmd_files)
@@ -125,6 +124,7 @@ endif
 
 endif # skip-inst
 
-.PHONY: $(PHONY)
 PHONY += FORCE
 FORCE: ;
+
+.PHONY: $(PHONY)