Sorry for replying so late.

Thus spoke Yaakov (Cygwin/X):
> On Mon, 2011-02-07 at 10:50 +0100, Fabiano Sidler wrote:
> > I'm trying to build a cross-compiler under Linux and MacOSX using this
> > script: http://sourceware.org/ml/cygwin/2010-08/txt00010.txt
> > I get the same error on Linux and MacOSX after the make of line 340:
> 
> Cygwin normally builds with -Werror but there are a few warnings
> generated by GCC 4.5 which haven't been fixed yet in the code.  Remove
> -Werror from $top_builddir/i686-pc-cygwin/winsup/cygwin/Makefile and the
> rest of the build should precede without any further difficulties.

Not without any further difficulties, but at least with a different error:

=== snip ===
[...]
/opt/devel/cygwin/src/cygwin-1.7.6-1/winsup/utils/mingw i686-pc-cygwin-gcc -c -D
__CRTDLL__ -U__MSVCRT__ -g -O2 -Wno-error -I/opt/devel/cygwin/src/cygwin-1.7.6-1
/winsup/mingw/include -I/opt/devel/cygwin/src/cygwin-1.7.6-1/winsup/mingw/../inc
lude -nostdinc -iwithprefixbefore include -I /opt/devel/cygwin/src/cygwin-1.7.6-
1/winsup/mingw/../w32api/include /opt/devel/cygwin/src/cygwin-1.7.6-1/winsup/min
gw/crt1.c -o crt1.o
/opt/devel/cygwin/src/cygwin-1.7.6-1/winsup/utils/mingw: couldn't find i686-pc-m
ingw32 directory
make[3]: *** [crt1.o] Error 1
make[3]: Leaving directory `/opt/devel/cygwin/build/cygwin/i686-pc-cygwin/winsup
/mingw'
make[2]: *** [mingw] Error 1
make[2]: Leaving directory `/opt/devel/cygwin/build/cygwin/i686-pc-cygwin/winsup
'
make[1]: *** [all-target-winsup] Error 2
make[1]: Leaving directory `/opt/devel/cygwin/build/cygwin'
make: *** [all] Error 2
=== snap ===

Again, the same error on Linux and OSX.

Thank you for helping, btw! ;)

Greetings,
Fabiano