Problem with winebuild under cygwin

I am trying to build Wine cvs under Cygwin and when trying to build dlls
I get this error:
 
../tools/winebuild/winebuild  -o advapi32/advapi32.spec.def --def
advapi32/advapi32.spec
Unable to create output file '(null)'
make: *** [advapi32/advapi32.spec.def] Error 1
 
 
Does someone have any idea on how to fix that ?
 
Julien

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