When pkg-config is built for Windows, it will override the .pc file's prefix variable by detecting where the .pc file is actually installed. This is because Windows users are not expected to follow a fixed directory tree like on Unix. Users then are likely to have different paths than the paths built into the .pc file. Overriding the prefix allows the .pc file to be relocatable even when the builder had no intention of it.

This relocatable feature would be useful everywhere, though. It should be made available on all platforms, but continue to default to on only for Windows. The --dont-define-prefix option already exists for Windows, so the expected reverse option would be --define-prefix.