gplugin/gplugin

Fix the build when ran in a meson subproject.
feature/meson-subproject-fix
2019-08-12, Gary Kramlich
923cbd2a8055
Fix the build when ran in a meson subproject.

We were using meson.build_root() when we should have been using
meson.current_build_dir().
<?xml version="1.0" encoding="UTF-8"?>
<gresources>
<gresource prefix="/org/bitbucket/gplugin/gplugin/viewer/">
<file compressed="true">window.ui</file>
</gresource>
</gresources>