meson: fix building screen-share module

When building screen-share module with meson loading the module
fails with:
  [00:01:28.604] Failed to load module: /usr/local/lib/weston/screen-share.so: undefined symbol: os_create_anonymous_file
  Failed to process Wayland connection: Broken pipe
  failed to create display: Broken pipe

The function os_create_anonymous_file is defined in libshared,
adding libshared to the dependency makes sure the function gets
compiled into screen-share.so.

Fixes: wayland/weston#208



Signed-off-by: Stefan Agner <stefan@agner.ch>

compositor/meson.build

@@ -61,6 +61,7 @@ if get_option('screenshare')
 		fullscreen_shell_unstable_v1_protocol_c,
 	]
 	deps_screenshare = [
+		dep_libshared,
 		dep_libweston,
 		dep_wayland_client,
 	]