Hello Michal,

I waited some days for a fix - but obviously no one else has this 
problem so far ...

This merge

"Merge branch 'kbuild' of 
git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild"

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=84d69848c97faab0c25aa2667b273404d2e2a64a

creates a bunch of warnings on my system and the built kernel does not 
boot (it complains about a missing root fs).

In the build process some .ko files are built fine and some don't:

(..)
   MODPOST 176 modules
   AS      arch/x86/boot/compressed/efi_thunk_64.o
   GZIP    arch/x86/boot/compressed/vmlinux.bin.gz
   CC      arch/x86/boot/compressed/misc.o
WARNING: "memset" [sound/usb/snd-usbmidi-lib.ko] has no CRC!
WARNING: "__fentry__" [sound/usb/snd-usbmidi-lib.ko] has no CRC!
WARNING: "memcpy" [sound/usb/snd-usbmidi-lib.ko] has no CRC!
WARNING: "__sw_hweight32" [sound/usb/snd-usbmidi-lib.ko] has no CRC!
WARNING: "_copy_to_user" [sound/usb/snd-usb-audio.ko] has no CRC!
WARNING: "memset" [sound/usb/snd-usb-audio.ko] has no CRC!
WARNING: "__put_user_1" [sound/usb/snd-usb-audio.ko] has no CRC!
WARNING: "__put_user_4" [sound/usb/snd-usb-audio.ko] has no CRC!
WARNING: "__fentry__" [sound/usb/snd-usb-audio.ko] has no CRC!
WARNING: "memcpy" [sound/usb/snd-usb-audio.ko] has no CRC!
WARNING: "__fentry__" [sound/soundcore.ko] has no CRC!
(..)
WARNING: "__fentry__" [arch/x86/crypto/crc32c-intel.ko] has no CRC!
WARNING: "__fentry__" [arch/x86/crypto/crc32-pclmul.ko] has no CRC!
WARNING: "__fentry__" [arch/x86/crypto/aesni-intel.ko] has no CRC!
WARNING: "__fentry__" [arch/x86/crypto/aes-x86_64.ko] has no CRC!
   CC      arch/x86/crypto/aes-x86_64.mod.o
   CC      arch/x86/crypto/aesni-intel.mod.o
   CC      arch/x86/crypto/crc32-pclmul.mod.o
   CC      arch/x86/crypto/crc32c-intel.mod.o
(..)

When reverting the entire pull with

git diff 84d69848c97faab0c25aa2667b273404d2e2a64a 
d4d24d2d0a7ea3b62efd7336bfc2344e29b36bc5 | patch -p1

everything is ok again.

My system is a Debian Stretch.
gcc version 6.2.0 20161010 (Debian 6.2.0-6)

.config is attached - in the case I have an unusual one from your 
perspective.

Regards,
Oliver