gnu: inkscape: Add the glib-or-gtk-build-system phases.

This fixes an issue where an improperly set XDG_DATA_DIRS environment variable
would cause a segfault when opening the 'Save As' menu of Inkscape.  See:
<https://lists.gnu.org/archive/html/help-guix/2020-06/msg00093.html

>.

* gnu/packages/inkscape.scm (inkscape-1.0)[arguments]: Import the
(guix build glib-or-gtk-build-system) module.
[phases]: Add the glib-or-gtk-compile-schemas and glib-or-gtk-wrap phases.

Reported-by: Thorsten Wilms <t_w_@freenet.de>