selftests/powerpc: Specify we expect to build with std=gnu99

[Michael Ellerman]

On Fri, 2016-29-07 at 10:48:09 UTC, Michael Ellerman wrote:
> We have some tests that assume we're using std=gnu99, which is fine on
> most compilers, but some old compilers use a different default.
> 
> So make it explicit that we want to use std=gnu99.
> 
> Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>

Applied to powerpc fixes.

https://git.kernel.org/powerpc/c/ca49e64f0cb1368fc666a53b16

cheers