Instead of attempting to figure out what the paths will be, take the
returned file object and pass that around, meson will then automatically
figure out the correct paths.
The latter doesn't work correctly when being used as a subproject, as it
returns the *absolute* root. So if pkgconf is being built as part of
muon, then it will return muon's source root. current_source_dir, on the
other hand returns the directory correctly whether being built as a
subproject or superproject.
Eli Schwartz
Dylan Baker
Ariadne Conill