"Johnny C. Lam" wrote:

> I've seen many configure scripts that conditionally set certain
> ac_cv_* values depending on whether other libraries were found or not.

  That's okay.  The point is that all these ac_cv_* then are present in
config.cache and can easily be set to "no" by a post-processing script. 
That's a lot easier than parsing the configure script itself by such a
script in order to create config.cache.

  Cheers
      ,
   Rene