how do I set pkgconfig to use /usr/lib64 ?

[sean darcy]

I'm running x86_64 fc3. All the 64bit apps put the pkgconfig files in 
/usr/lib64. When I'm building a program I often forget to export  
PKG_CONFIG_PATH=/usr/lib64/pkgconfig:/usr/lib/pkgconfig.

Now I did put it in rc.local. That didn't work. Given that I and others use 
a lot of user names, is there someplace to change PKG_CONFIG_PATH 
universally?  Where is it set to /usr/lib/pkgconfig in the first place?

thanks
sean