Attached two patches fixing the output of pc_path, pc_system_includedirs
& pc_system_libdirs. They are supposed to output the compile time path,
and not change based on runtime config. More detailed information
available on the commit messages.

N.B: the win32 changes are entirely untested.

- NRK

All merged, thanks, NRK!

Before looking, I was concerned your changes would set pc_path to a static 
string on Windows as well, but you correctly kept the pkg-config.exe path 
as the "compiled-in" string, which is the appropriate, analogous behavior. 
In its original context, pkg-config, and the toolchain sysroot in general, 
are not designed to be relocatable, unlike a "portable" Win32 application. 
(Kind of a shame, because it would be useful if I could install, say, .deb 
packages into "$HOME/.local/" as a regular user.)