Make granite-demo optional (#676)

We don't need demo in the Flatpak Platform for example,
so disabling demo when building for Flatpak should lessen its size
and make build time faster a little

meson.build

@@ -65,13 +65,16 @@ i18n = import('i18n')
 
 subdir('lib')
 subdir('data')
-subdir('demo')
 subdir('po')
 
 if get_option('documentation')
     subdir('doc')
 endif
 
+if get_option('demo')
+    subdir('demo')
+endif
+
 # set up post-install script to refresh the GTK icon cache
 meson.add_install_script(
     join_paths(meson.current_source_dir(), 'meson', 'post_install.py'),

meson_options.txt

@@ -1,2 +1,3 @@
 option('documentation', type: 'boolean', value: false, description: 'generate documentation with gtk-doc and valadoc')
 option('introspection', type: 'boolean', value: true, description: 'Whether to build introspection files')
+option('demo', type: 'boolean', value: true, description: 'Whether to build granite-demo')