[Bug bootstrap/56645] libgcc /configure identifies non-existing /lib/cpp as preprocessor on Mingw

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56645

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> 2013-03-18 11:20:12 UTC ---
I think the issue is that

checking for /c/Devel/gcc-cvs.not/build_native/./gcc/xgcc
-B/c/Devel/gcc-cvs.not/build_native/./gcc/
-L/c/Devel/gcc-cvs.not/build_native/mingw32/winsup/mingw
-L/c/Devel/gcc-cvs.not/build_native/mingw32/winsup/w32api/lib -isystem
/c/Devel/gcc-cvs.not/gcc-4.8.0-RC-20130316/winsup/mingw/include -isystem
/c/Devel/gcc-cvs.not/gcc-4.8.0-RC-20130316/winsup/w32api/include
-B/mingw/local/mingw32/bin/ -B/mingw/local/mingw32/lib/ -isystem
/mingw/local/mingw32/include -isystem /mingw/local/mingw32/sys-include   
option to accept ISO C89... unsupported

fails.  This likely results in -E and -E -traditional-cpp to fail as well
and fallback to /lib/cpp.

Figure out why

----
/* end confdefs.h.  */
#ifdef __STDC__
# include <limits.h>
#else
# include <assert.h>
#endif
                     Syntax error
----

does not work.