Build using O=path

[me@tobin.cc (Tobin C. Harding)]

Hi,

I'm unable to build the kernel using the O=path/to/out option.  Am I
doing something brain dead?

$ cd $KERNEL
$ make mrproper
$ cp path/to/valid/config/file .config
$ make O=/abs/path/to/output
...
scripts/kconfig/conf  --syncconfig Kconfig
***
*** Configuration file ".config" not found!
***
*** Please run some configurator (e.g. "make oldconfig" or
*** "make menuconfig" or "make xconfig").
...

So I tried copying the .config file to the output directory

$ cp .config /abs/path/to/output
$ make O=/abs/path/to/output
...
  Using /home/tobin/build/kernel/linux as source for kernel
  /home/tobin/build/kernel/linux is not clean, please run 'make mrproper'
  in the '/home/tobin/build/kernel/linux' directory.
/home/tobin/build/kernel/linux/Makefile:1091: recipe for target 'prepare3' failed
make[1]: *** [prepare3] Error 1
make[1]: Leaving directory '/home/tobin/build/kernel/output/master'
Makefile:146: recipe for target 'sub-make' failed
make: *** [sub-make] Error 2


Same thing if I use KBUILD_OUTPUT instead of passing O=


thanks,
Tobin.