selftests/powerpc: Fix standalone powerpc build

[Michael Ellerman]

On Mon, 2017-03-27 at 04:19:47 UTC, Michael Ellerman wrote:
> The changes to enable building with a separate output directory, in
> commit a8ba798bc8ec ("selftests: enable O and KBUILD_OUTPUT") broke
> building the powerpc selftests on their own, eg:
> 
>  $ cd tools/testing/selftests/powerpc; make
> 
> It was partially fixed in commit e53aff45c490 ("selftests: lib.mk Fix
> individual test builds"), which defined OUTPUT for standalone tests. But
> that only defines OUTPUT within the Makefile, the value is not exported
> so sub-shells can't see it. We could export OUTPUT, but it's actually
> cleaner to just expand the value of OUTPUT before we invoke the shell.
> 
> Fixes: a8ba798bc8ec ("selftests: enable O and KBUILD_OUTPUT")
> Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>

Applied to powerpc fixes.

https://git.kernel.org/powerpc/c/2db2c250dd3d1e74a50d4ab5f44c44

cheers