Pull Kbuild updates from Masahiro Yamada:
"Build system:

- add CONFIG_UNUSED_KSYMS_WHITELIST, which will be useful to define a
fixed set of export symbols for Generic Kernel Image (GKI)

- allow to run 'make dt_binding_check' without .config

- use full schema for checking DT examples in *.yaml files

- make modpost fail for missing MODULE_IMPORT_NS(), which makes more
sense because we know the produced modules are never loadable

- Remove unused 'AS' variable

Kconfig:

- sanitize DEFCONFIG_LIST, and remove ARCH_DEFCONFIG from Kconfig
files

- relax the 'imply' behavior so that symbols implied by 'y' can
become 'm'

- make 'imply' obey 'depends on' in order to make 'imply' really weak

Misc:

- add documentation on building the kernel with Clang/LLVM

- revive __HAVE_ARCH_STRLEN for 32bit sparc to use optimized strlen()

- fix warning from deb-pkg builds when CONFIG_DEBUG_INFO=n

- various script and Makefile cleanups"

* tag 'kbuild-v5.7' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (34 commits)
Makefile: Update kselftest help information
kbuild: deb-pkg: fix warning when CONFIG_DEBUG_INFO is unset
kbuild: add outputmakefile to no-dot-config-targets
kbuild: remove AS variable
net: wan: wanxl: refactor the firmware rebuild rule
net: wan: wanxl: use $(M68KCC) instead of $(M68KAS) for rebuilding firmware
net: wan: wanxl: use allow to pass CROSS_COMPILE_M68k for rebuilding firmware
kbuild: add comment about grouped target
kbuild: add -Wall to KBUILD_HOSTCXXFLAGS
kconfig: remove unused variable in qconf.cc
sparc: revive __HAVE_ARCH_STRLEN for 32bit sparc
kbuild: refactor Makefile.dtbinst more
kbuild: compute the dtbs_install destination more simply
Makefile: disallow data races on gcc-10 as well
kconfig: make 'imply' obey the direct dependency
kconfig: allow symbols implied by y to become m
net: drop_monitor: use IS_REACHABLE() to guard net_dm_hw_report()
modpost: return error if module is missing ns imports and MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS=n
modpost: rework and consolidate logging interface
kbuild: allow to run dt_binding_check without kernel configuration
...