check mips abi x linker emulation compatibility

[Eric Christopher]

> I've no strong objection to adding another flag, but I think we should
> still keep the existing tests to make sure that configurations like
> mips-elf and mips64-elf are ABI-neutral by default.  That's always
> been their traditional behaviour.

It looks like for the tests if we're running on a hosted target that we
need to explicitly add the abi, otherwise we get the default. Alex could
probably come up with a variable to add options to the tests...

-eric

-- 
Eric Christopher <echristo@redhat.com>