configuration bug

I'm trying to compile GiNaC on a PC running Windows 2000 with the Cygwin UNIX utilities, but there seems to be a problem with the directories. When I compile CLN and make install, the CLN files get installed in /usr/local/lib and /usr/local/include by default. This seems like a sensible place to put the files, but when I run ./configure in the GiNaC directory, it tells me configure: error: cannot find header for Bruno Haible's CLN This message goes away if I install the CLN files in /usr/include and /usr/lib, but I don't like to do it this way. Do you know how I can make the configure script look for the CLN files in their default location in /usr/local? Thanks, Issac