xwayland: override Meson dependency

This allows developers to setup Xwayland as a subproject of a
Wayland compositor, and have it correctly pick up the features
advertised in the dependency variables.

Signed-off-by: Simon Ser <contact@emersion.fr>

hw/xwayland/meson.build

@@ -159,15 +159,7 @@ xwayland_server = executable(
     install_dir: xwayland_path
 )
 
-pkgconfig = import('pkgconfig')
-
-pkgconfig.generate(
-    filebase: 'xwayland',
-    name: 'Xwayland',
-    description: 'X Server for Wayland',
-    variables: [
-        'exec_prefix=${prefix}',
-        'xwayland=' + xwayland_path + '/Xwayland',
+xwayland_vars = [
     'have_glamor=' + build_glamor.to_string(),
     'have_eglstream=' + build_eglstream.to_string(),
     'have_initfd=true',
@@ -181,7 +173,18 @@ pkgconfig.generate(
     'have_host_grab=true',
     'have_decorate=' + have_libdecor.to_string(),
     'have_byteswappedclients=true',
-    ],
+]
+
+pkgconfig = import('pkgconfig')
+
+pkgconfig.generate(
+    filebase: 'xwayland',
+    name: 'Xwayland',
+    description: 'X Server for Wayland',
+    variables: [
+        'exec_prefix=${prefix}',
+        'xwayland=' + xwayland_path + '/Xwayland',
+    ] + xwayland_vars,
 )
 
 xwayland_manpage = configure_file(
@@ -194,3 +197,13 @@ install_man(xwayland_manpage)
 datadir = join_paths(get_option('prefix'), get_option('datadir'))
 desktopdir = join_paths(datadir, 'applications')
 install_data('desktop/org.freedesktop.Xwayland.desktop', install_dir : desktopdir)
+
+if meson.version().version_compare('>= 0.56.0')
+    meson.override_find_program('Xwayland', xwayland_server)
+
+    meson.override_dependency('xwayland', declare_dependency(
+        variables: [
+            'xwayland=' + xwayland_server.full_path(),
+        ] + xwayland_vars,
+    ))
+endif