girdir pc variable changes
It seems !63 (merged) added some behavioral changes on the girdir .pc variable, which apparently broke (just?) Tracker in nightly builds, eg: http://sdkbuilder.gnome.org/logs/build-2018-10-09-171557/build-gnome-apps-nightly-master-org.gnome.Totem-x86_64.txt
Tracker does rely on path substitutions for the gir dir: https://gitlab.gnome.org/GNOME/tracker/blob/master/meson.build#L316
AFAICS there's two changes:
- In meson, the variable started depending on ${prefix} instead of ${datadir}
- In autotools, the variable is now fully expanded, and does not allow path substitutions.
The former is arguably a positive change seeing the problem described in that MR, but makes it troublesome for projects to work nicely on top of old and new variables. The latter is harsher, as there is no way to both rely on this pkgconfig variable and install in another prefix.