ci: Release with vendored libglnx and variant-schema-compiler

We now have subprojects for a few dependencies. libglnx and
variant-schema-compiler used to be git subtrees and we recommend
distributions to use those vendored dependencies. We turned them into
meson wraps, which means they are no longer vendored in. We can include
them with --include-subprojects, but then we have to make sure that the
subprojects we recommend to use from the system (bwrap and
xdg-dbus-proxy) are disabled.

.github/workflows/release.yml

@@ -37,8 +37,10 @@ jobs:
 
       - name: Build flatpak
         run: |
-          meson setup _build
-          meson dist -C _build
+          meson setup _build \
+            -Dsystem_bubblewrap=bwrap \
+            -Dsystem_dbus_proxy=xdg-dbus-proxy
+          meson dist -C _build --include-subprojects
 
       - name: Extract release information
         run: |