This is a new attempt at the PR libgcj/40868 [1].

This time around a compiler variable is introduced in configure.ac and
Makefile.am is patched as well.

This has been tested with build/host=linux-gnu target=i686-w64-mingw32.
This has not been tested with a canadian-cross but "it should just work".

[1] http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40868