gi: fix build of pango from subprojects
Projects like pango depending on fontconfig-2.0.gir or any other gir provided by gobject-introspection in its sources directory need to pass this directory as an extra include dir search path.
Projects like pango depending on fontconfig-2.0.gir or any other gir provided by gobject-introspection in its sources directory need to pass this directory as an extra include dir search path.