[libstdc++] Use LD_RUN_PATH when linking abi_check

[Benjamin Kosnik]

> > Have a look at libstdc++-v3/testsuite/lib/libstdc++-v3-dg.exp
> > (libstdc++-v3-init): setting LD_LIBRARYN32_PATH and LD_LIBRARY64_PATH to
> > the same value (and probably SHLIB_PATH for HP-UX) should be enough.
> 
> Huh.  We have to do that same logic, then, involving multilibs and libgcc_s.
> 
> Instead of putting all that into Makefile.am, I'm putting it as another
> option in testsuite_flags.  Comments solicited.

Man. If only the multi-libs and crosses were built with staged includes
and libraries... a lot of this Irix hackery would be greatly simplified.

> > Speaking of LD_LIBRARY64_PATH: make check-abi currently doesn't cater for
> > multilibbed systems like Solaris 8 and IRIX 6.  I suggest placing
> > baseline_symbols.txt in the corresponding subdirs of config/abi (like
> > sparc-sun-solaris2.8/sparcv9 and mips-sgi-irix6.5/mabi=64) and running
> > abi_check for every multilib.  I'm low on time for gcc hacking lately, so I
> > haven't yet figured out how to do so.
> 
> Running for each multilib is a good idea, although I'd prefer not to have
> more nested subdirectories, with one file in each dir.  I'll add this to
> the todo list.

Um. Isn't 'make check-abi' only useful for systems that are actually
using versioning, like BSD and Linux? I'm not aware of other platforms
that actually are using symbol versioning. 

Perhaps it is useful, but that was not the intention of this Makefile
rule.

Must be missing something,
benjamin