Kbuild updates for v5.18

- Add new environment variables, USERCFLAGS and USERLDFLAGS to allow
    additional flags to be passed to user-space programs.
 
  - Fix missing fflush() bugs in Kconfig and fixdep
 
  - Fix a minor bug in the comment format of the .config file
 
  - Make kallsyms ignore llvm's local labels, .L*
 
  - Fix UAPI compile-test for cross-compiling with Clang
 
  - Extend the LLVM= syntax to support LLVM=<suffix> form for using a
    particular version of LLVm, and LLVM=<prefix> form for using custom
    LLVM in a particular directory path.
 
  - Clean up Makefiles
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Merge tag 'kbuild-v5.18-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild updates from Masahiro Yamada:

 - Add new environment variables, USERCFLAGS and USERLDFLAGS to allow
   additional flags to be passed to user-space programs.

 - Fix missing fflush() bugs in Kconfig and fixdep

 - Fix a minor bug in the comment format of the .config file

 - Make kallsyms ignore llvm's local labels, .L*

 - Fix UAPI compile-test for cross-compiling with Clang

 - Extend the LLVM= syntax to support LLVM=<suffix> form for using a
   particular version of LLVm, and LLVM=<prefix> form for using custom
   LLVM in a particular directory path.

 - Clean up Makefiles

* tag 'kbuild-v5.18-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  kbuild: Make $(LLVM) more flexible
  kbuild: add --target to correctly cross-compile UAPI headers with Clang
  fixdep: use fflush() and ferror() to ensure successful write to files
  arch: syscalls: simplify uapi/kapi directory creation
  usr/include: replace extra-y with always-y
  certs: simplify empty certs creation in certs/Makefile
  certs: include certs/signing_key.x509 unconditionally
  kallsyms: ignore all local labels prefixed by '.L'
  kconfig: fix missing '# end of' for empty menu
  kconfig: add fflush() before ferror() check
  kbuild: replace $(if A,A,B) with $(or A,B)
  kbuild: Add environment variables for userprogs flags
  kbuild: unify cmd_copy and cmd_shipped

usr/Makefile

@@ -3,7 +3,7 @@
 # kbuild file for usr/ - including initramfs image
 #
 
-compress-y					:= shipped
+compress-y					:= copy
 compress-$(CONFIG_INITRAMFS_COMPRESSION_GZIP)	:= gzip
 compress-$(CONFIG_INITRAMFS_COMPRESSION_BZIP2)	:= bzip2
 compress-$(CONFIG_INITRAMFS_COMPRESSION_LZMA)	:= lzma
@@ -37,7 +37,7 @@ endif
 # .cpio.*, use it directly as an initramfs, and avoid double compression.
 ifeq ($(words $(subst .cpio.,$(space),$(ramfs-input))),2)
 cpio-data := $(ramfs-input)
-compress-y := shipped
+compress-y := copy
 endif
 
 endif

usr/include/Makefile

@@ -10,7 +10,10 @@ UAPI_CFLAGS := -std=c90 -Wall -Werror=implicit-function-declaration
 
 # In theory, we do not care -m32 or -m64 for header compile tests.
 # It is here just because CONFIG_CC_CAN_LINK is tested with -m32 or -m64.
-UAPI_CFLAGS += $(filter -m32 -m64, $(KBUILD_CFLAGS))
+UAPI_CFLAGS += $(filter -m32 -m64 --target=%, $(KBUILD_CFLAGS))
+
+# USERCFLAGS might contain sysroot location for CC.
+UAPI_CFLAGS += $(USERCFLAGS)
 
 override c_flags = $(UAPI_CFLAGS) -Wp,-MMD,$(depfile) -I$(objtree)/usr/include
 
@@ -84,7 +87,7 @@ endif
 # asm-generic/*.h is used by asm/*.h, and should not be included directly
 no-header-test += asm-generic/%
 
-extra-y := $(patsubst $(obj)/%.h,%.hdrtest, $(shell find $(obj) -name '*.h' 2>/dev/null))
+always-y := $(patsubst $(obj)/%.h,%.hdrtest, $(shell find $(obj) -name '*.h' 2>/dev/null))
 
 # Include the header twice to detect missing include guard.
 quiet_cmd_hdrtest = HDRTEST $<