New review comment by oreo639 on void-packages repository

https://github.com/void-linux/void-packages/pull/48982#discussion_r1505491663

Comment:
Yeah, just replace it with `join_paths('${datadir}', 'gir-1.0')`.

(`pc_sysrootdir` gets expanded as `/` when native compiling and `${XBPS_CROSS_BASE}` when cross compiling, meson doesn't generate a default `datadir` for absolute paths)