Ignoring .pc files in default pkgconfig path

[Tomas Carnecky]

I want pkg-config to ignore all .pc files in the default pkgconfig path. 
I'm installing packages into a separate prefix, and I want to make sure 
none of the packages installed by the system package manager are pulled 
in. So I'd rather have the build process fail if the package isn't 
installed in the separate prefix then having the system package pulled 
in. Is that possible? I don't see any such option in the man page.

tom