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

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
  ...

diff --cc Kbuild
Simple merge

diff --cc Makefile
index ccb7d5b2fbf5f904b780ec792ef7c47c5c44a618,06a5798335fcdb75c8211d537f595193a01bbb01..efb942ad0b556c9fc3eb4636f39a351425a8cedc
--- 1/Makefile
--- 2/Makefile
+++ b/Makefile
@@@ -621,6 -602,12 +604,11 @@@ endi
  # Defaults to vmlinux, but the arch makefile usually adds further targets
  all: vmlinux
  
 -CFLAGS_KCOV   := $(call cc-option,-fsanitize-coverage=trace-pc,)
+ KBUILD_CFLAGS += $(call cc-option,-fno-PIE)
+ KBUILD_AFLAGS += $(call cc-option,-fno-PIE)
+ CFLAGS_GCOV   := -fprofile-arcs -ftest-coverage -fno-tree-loop-im $(call cc-disable-warning,maybe-uninitialized,)
+ export CFLAGS_GCOV CFLAGS_KCOV
+ 
  # The arch Makefile can set ARCH_{CPP,A,C}FLAGS to override the default
  # values of the respective KBUILD_* variables
  ARCH_CPPFLAGS :=

diff --cc arch/arm/Makefile
Simple merge

diff --cc arch/hexagon/Makefile
Simple merge

diff --cc arch/x86/entry/vdso/Makefile
Simple merge

diff --cc scripts/Makefile.asm-generic
Simple merge

diff --cc scripts/Makefile.build
Simple merge

diff --cc scripts/Makefile.headersinst
Simple merge

diff --cc scripts/Makefile.host
Simple merge

diff --cc scripts/Makefile.lib
Simple merge

diff --cc scripts/Makefile.modpost
Simple merge

diff --cc scripts/link-vmlinux.sh
Simple merge

diff --cc scripts/mkcompile_h
Simple merge