rules: Build all extensions via the upstream build system

We don't need to hardcode the list to build, as the build system
provides a way to build 'all' extensions.

debian/rules

@@ -1,17 +1,9 @@
 #!/usr/bin/make -f
 
-EXTENSIONS_ENABLED='apps-menu, places-menu, \
- launch-new-instance, window-list, \
- drive-menu, screenshot-window-sizer, \
- windowsNavigator, workspace-indicator, \
- auto-move-windows, native-window-placement, user-theme'
-
-EXTENSIONS_DISABLED='example'
-
 %:
 	dh $@ --with gnome
 
 override_dh_auto_configure:
 	dh_auto_configure -- \
-		-Denable_extensions=$(EXTENSIONS_ENABLED) \
+		-Dextension_set=all \
 		-Dclassic_mode=true