meson: override dependencies to ease use as subproject

Make it easier to use Wayland as a Meson subproject by overriding
dependencies we define. This allows to easily build Wayland as a
subproject like so:

    subproject('wayland', required: false, default_options: ['documentation=false'])

After this statement, the wayland-* dependencies will use the subproject
instead of the system if available.

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

cursor/meson.build

@@ -36,3 +36,12 @@ pkgconfig.generate(
 	libraries: wayland_cursor,
 	filebase: 'wayland-cursor',
 )
+
+wayland_cursor_dep = declare_dependency(
+	link_with: wayland_cursor,
+	include_directories: [ root_inc, include_directories('.') ],
+)
+
+if meson.version().version_compare('>= 0.54.0')
+	meson.override_dependency('wayland-cursor', wayland_cursor_dep)
+endif

egl/meson.build

@@ -41,3 +41,12 @@ pkgconfig.generate(
 	description: 'Backend wayland-egl interface',
 	version: '3'
 )
+
+wayland_egl_dep = declare_dependency(
+	link_with: wayland_egl,
+	include_directories: [ root_inc, include_directories('.') ],
+)
+
+if meson.version().version_compare('>= 0.54.0')
+	meson.override_dependency('wayland-egl', wayland_egl_dep)
+endif

src/meson.build

@@ -207,6 +207,10 @@ if get_option('libraries')
 		]
 	)
 
+	if meson.version().version_compare('>= 0.54.0')
+		meson.override_dependency('wayland-server', wayland_server_dep)
+	endif
+
 	wayland_client = library(
 		'wayland-client',
 		sources: [
@@ -251,6 +255,10 @@ if get_option('libraries')
 		]
 	)
 
+	if meson.version().version_compare('>= 0.54.0')
+		meson.override_dependency('wayland-client', wayland_client_dep)
+	endif
+
 	install_headers([
 		'wayland-util.h',
 		'wayland-server.h',