kbuild: ARCH=um archheaders failed

[Randy Dunlap]

Hi Yamada-san,

I see this every few weeks.  It's not reproducible (it depends
on the moon, Mars, etc.).

I'm using O=builddir.  The build log is short (below).

Do you see a makefile problem here?  (nothing to do with mmotm;
I see it more frequently with linux-next since I do many daily
builds with it)


thanks.
-- 
make[1]: Entering directory '/home/rdunlap/mmotm-2018-0802-1529/UM64'
  UPD     include/generated/uapi/linux/version.h
  WRAP    arch/x86/include/generated/asm/dma-contiguous.h
  WRAP    arch/x86/include/generated/asm/export.h
  WRAP    arch/x86/include/generated/asm/early_ioremap.h
  WRAP    arch/x86/include/generated/asm/mcs_spinlock.h
  WRAP    arch/x86/include/generated/asm/mm-arch-hooks.h
  WRAP    arch/x86/include/generated/uapi/asm/bpf_perf_event.h
  WRAP    arch/x86/include/generated/uapi/asm/poll.h
  GEN     ./Makefile
make[2]: *** No rule to make target 'archheaders'.  Stop.
arch/um/Makefile:119: recipe for target 'archheaders' failed
make[1]: *** [archheaders] Error 2
make[1]: *** Waiting for unfinished jobs....
  UPD     include/config/kernel.release
make[1]: *** wait: No child processes.  Stop.
Makefile:146: recipe for target 'sub-make' failed
make: *** [sub-make] Error 2