Pull Kbuild updates from Masahiro Yamada:

 - Add -s option (strict mode) to merge_config.sh to make it fail when
   any symbol is redefined.

 - Show a warning if a different compiler is used for building external
   modules.

 - Infer --target from ARCH for CC=clang to let you cross-compile the
   kernel without CROSS_COMPILE.

 - Make the integrated assembler default (LLVM_IAS=1) for CC=clang.

 - Add <linux/stdarg.h> to the kernel source instead of borrowing
   <stdarg.h> from the compiler.

 - Add Nick Desaulniers as a Kbuild reviewer.

 - Drop stale cc-option tests.

 - Fix the combination of CONFIG_TRIM_UNUSED_KSYMS and CONFIG_LTO_CLANG
   to handle symbols in inline assembly.

 - Show a warning if 'FORCE' is missing for if_changed rules.

 - Various cleanups

* tag 'kbuild-v5.15' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (39 commits)
  kbuild: redo fake deps at include/ks...