Problem to configure --with-ns with GNUstep

[Germán Arias]

OK, now I have gcc 4.6 and I'm back to try emacs with gnustep. But now,
I'm unable to configure emacs. With 

./configure --with-ns --with-gnustep-conf=/etc/GNUstep/GNUstep.conf

I get the error:

checking AppKit/AppKit.h usability... no
checking AppKit/AppKit.h presence... no
checking for AppKit/AppKit.h... no
configure: error: `--with-ns' was specified, but the include
  files are missing or cannot be compiled

The file GNUstep.conf is read, and the path to AppKit/AppKit.h is found
successfully (I checked). But then the function
"ac_fn_c_check_header_mongrel" return errors. So, adding flags
(CPPFLAGS=-I/...) don't solve the problem, because even when the paths
are right, the function "ac_fn_c_check_header_mongrel" return errors.
Since I'm not an expert in scripts any advice is appreciated. Thanks.