Usage:
pkgconfig.generate(
...
description : 'A library with custom variables.',
variables : ['foo=bar', 'datadir=${prefix}/data']
)
The variables 'prefix', 'libdir' and 'includedir' are reserved, meson will
fail with an error message.
Variables can reference each other with the pkgconfig notation, e.g.
variables : ['datadir=${prefix}/data',
'otherdatadir=${datadir}/other']
meson does not check this for correctness or that the referenced variable
exists, we merely keep the same order as specified.
This allows us to more easily have the documentation in sync with
the source code as people will have to document new features etc
right at the time where they implement it.