Supporting AC_TRY_RUN for cross-compilation (was: AC_FUNC_SETVBUF _REVERSED in cross-compilation)

[Dan Kegel]

Paul D. Smith wrote:
> AC_FUNC_SETVBUF_REVERSED macro has no option for how
> it behaves during cross-compilation.
> ...
> Anyone else have any good ideas?

Yes, we need to fix all the macros and config scripts that 
use AC_TRY_RUN to behave better, but that's a big job,
and even when we're done, we'll end up either requiring
users to override tests via the environment OR we'll have
defaults which are broken for some platforms.

Another path we should pursue in parallel: for those cases where 
the host system is on the network and available to run code,
autoconf should be able to take advantage of it.
IMHO it's time to bite the bullet and make AC_TRY_RUN
support cross-compilation better.  

How about this: configure should take a commandline argument,
--with-remote-run=, which specifies a wrapper command
which knows how to execute tests remotely.  For instance, 
--with-remote-run="ssh chassis" would use ssh to run the AC_TRY_RUN
test on machine 'chassis'.  If --with-remote-run is not
specified, AC_TRY_RUN would behave just as it does today.

This needs to be built into autoconf, not hacked in by
individual developers on demand, as has been done (and posted
about here) before.

I just checked, and ssh does pass back exit status properly,
at least for  /bin/true and /bin/false.

Comments?
- Dan