Build error with O= option

[Gioh Kim]

Hi,

I am trying to use O=<dir> option when building kernel.
It failed with missing .config file error.
I checked out the message and found out it tried to read .config in
the output directory.

It's strange because there is no command to copy .config to the output
directory.
I tested v4.14 and v4.15, and both failed.

I googled that error message and found one thread in the stackoverflow:
https://stackoverflow.com/questions/28603372/kernel-compilation-not-finding-config-file

Is it two years old but not fixed yet?
Or did I use O= option wrong?
FYI, following is my error message.


gohkim at ws00837:~/work/linux-torvalds$ make O=./output V=1
make -C /home/gohkim/work/linux-torvalds/output
KBUILD_SRC=/home/gohkim/work/linux-torvalds \
-f /home/gohkim/work/linux-torvalds/Makefile
make[1]: Entering directory '/home/gohkim/work/linux-torvalds/output'
make -f ../scripts/Makefile.build obj=arch/x86/entry/syscalls all
make -f ../scripts/Makefile.build obj=scripts/basic
(cat /dev/null; ) > scripts/basic/modules.order
rm -f .tmp_quiet_recordmcount
make -f ../scripts/Makefile.build obj=arch/x86/tools relocs
make -f ../Makefile silentoldconfig
make -f ../scripts/Makefile.build obj=scripts/basic
(cat /dev/null; ) > scripts/basic/modules.order
rm -f .tmp_quiet_recordmcount
ln -fsn .. source
/bin/bash ../scripts/mkmakefile \
    .. . 4 15
  GEN     ./Makefile
make -f ../scripts/Makefile.build obj=scripts/kconfig silentoldconfig
mkdir -p include/config include/generated
test -e include/generated/autoksyms.h || \
    touch   include/generated/autoksyms.h
scripts/kconfig/conf  --silentoldconfig Kconfig
***
*** Configuration file ".config" not found!
***
*** Please run some configurator (e.g. "make oldconfig" or
*** "make menuconfig" or "make xconfig").
***
../scripts/kconfig/Makefile:38: recipe for target 'silentoldconfig' failed
make[3]: *** [silentoldconfig] Error 1
../Makefile:524: recipe for target 'silentoldconfig' failed
make[2]: *** [silentoldconfig] Error 2
/home/gohkim/work/linux-torvalds/Makefile:604: recipe for target
'include/config/auto.conf' failed
make[1]: *** [include/config/auto.conf] Error 2
make[1]: Leaving directory '/home/gohkim/work/linux-torvalds/output'
Makefile:146: recipe for target 'sub-make' failed
make: *** [sub-make] Error 2


-- 

Best regards,
Gioh Kim