Fix failure on powerpc 32-bit only targets

[Yann Droneaud]

Hi,

Le lundi 27 mai 2019 à 14:28 +0930, Alan Modra a écrit :
> Targets that lack ppc64 support were failing the new prefix-reloc
> test.  This patch adds some test infrastructure to deal with that,
> and
> changes the powerpc gas usage info so that "-a64" is omitted when
> unsupported.
> 
> I've been meaning to break up the usage message for a long time;
> While doing so causes translators some work now, it should make it
> easier next time a new powerpc option is added.
> 

It would be easier to review if usage message split was a seperate
patch.

Regards.

-- 
Yann Droneaud
OPTEYA