[lug] simplest way to change ./configure in a .src.rpm?

[D. Stimits]

I have an ncurses .src.rpm on RH 7.3 (KRUD) which I am rebuilding, but I 
want to change the spec file from configure option --without-debug to 
--with-debug. Running an rpm -i on the .src.rpm I can easily set it up 
to let me edit the spec, but of course the packaged .src.rpm, when I run 
  --rebuild on it, overwrites the version I had saved. What is the 
absolutely most simple way to edit that spec file, and run a rebuild on 
the rpm using the modifed spec file, under RH 7.3/KRUD?

D. Stimits, stimits AT attbi DOT com