core: Fix build with glib 2.30
core: Fix build with glib 2.30

gatispaeglis/ostree,leandrosansilva/ostree,sujitfulse/ostree,GNOME/ostree,sujitfulse/ostree,leandrosansilva/ostree,sujitfulse/ostree,resin-io/ostree,leandrosansilva/ostree,leandrosansilva/ostree,resin-io/ostree,GNOME/ostree,resin-io/ostree,sujitfulse/ostree,leandrosansilva/ostree,gatispaeglis/ostree,GNOME/ostree,GNOME/ostree,GNOME/ostree,resin-io/ostree,sujitfulse/ostree,gatispaeglis/ostree,gatispaeglis/ostree,gatispaeglis/ostree,gatispaeglis/ostree,resin-io/ostree