Problem with winebuild under cygwin

[Julien C]

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