Pull Kbuild fixes from Masahiro Yamada:
- detect missing missing "WITH Linux-syscall-note" for uapi headers
- fix needless rebuild when using Clang
- fix false-positive cc-option in Kconfig when using Clang
- avoid including corrupted .*.cmd files in the modpost stage
- fix warning of 'make vmlinux'
- fix {m,n,x,g}config to not generate the broken .config on the second
save operation.
- some trivial Makefile fixes
* tag 'kbuild-fixes-v5.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
kconfig: Clear "written" flag to avoid data loss
kbuild: Check for unknown options with cc-option usage in Kconfig and clang
lib/raid6: fix unnecessary rebuild of vpermxor*.c
kbuild: modpost: do not parse unnecessary rules for vmlinux modpost
kbuild: modpost: remove unnecessary dependency for __modpost
kbuild: modpost: handle KBUILD_EXTRA_SYMBOLS only for external modules
kbuild: modpost: include .*.cmd files only when targets exist
kbuild: initialize CLANG_FLAGS correctly in the top Makefile
kbuild: detect missing "WITH Linux-syscall-note" for uapi headers