Running the compat testsuite in "non-mirror" mode

[Eric Botcazou]

> Does this do the kind of thing you want?  This is just an example, not
> options I actually want to add for powerpc.

Looks perfect.  Let me give it a whirl tomorrow on SPARC though.

> Other files that set COMPAT_OPTIONS are lib/compat.exp,
> gcc.dg/compat/struct-layout-1.exp, and g++.dg/compat/compat.exp.  This
> continues to allow the default sets of options to be overridden.

I think this is the right granularity.  I'd like to be able to run the C 
compat testsuite twice, without necessarily doing the same for the 
struct-layout-1 testsuite.

-- 
Eric Botcazou