Add explicit dependency on "gucharmap-menus.ui"

This fixes building with muon.  Without it, glib-compile-resources fails
because it cannot find the source file "gucharmap-menus.ui" when
processing "gucharmap.gresource.xml".

---
 gucharmap/meson.build |    1 +
 1 file changed, 1 insertion(+)

Index: b/gucharmap/meson.build
===================================================================
--- a/gucharmap/meson.build
+++ b/gucharmap/meson.build
@@ -259,6 +259,7 @@ gucharmap_gtk3_sources += gnome.compile_
   'gucharmap-resources',
   'gucharmap.gresource.xml',
   c_name: 'gucharmap',
+  dependencies: files('gucharmap-menus.ui'),
 )
 
 gucharmap_gtk3_cppflags = disable_deprecated_cppflags + [