AC_TRY_RUN and cross-compiling

[Dan Kegel]

I just figured out how to make life easy for
cross-compiling.  configure should have an option,
--emit-try-run, which would generate and compile a C program
which, when compiled and run, would output environment
settings which could be used in future configure
runs to suppress AC_TRY_RUN's.  To use it,
you'd first run configure with that flag, 
transfer the generated try_run executable to
the host system by hand, run it, and save its output in, say, try_run.out.
Then you'd run configure again like this:
  `cat try_run.out` ../configure

This roughly mirrors what I'm doing by hand as I'm
trying to cross-compile glib...

Comments?
- Dan