Wayland: Add xdg-shell to the build system

src/CMakeLists.txt

@@ -39,6 +39,10 @@ elseif (_GLFW_WAYLAND)
                      linux_joystick.c posix_time.c posix_thread.c xkb_unicode.c
                      egl_context.c osmesa_context.c)
 
+    ecm_add_wayland_client_protocol(glfw_SOURCES
+        PROTOCOL
+        "${WAYLAND_PROTOCOLS_PKGDATADIR}/stable/xdg-shell/xdg-shell.xml"
+        BASENAME xdg-shell)
     ecm_add_wayland_client_protocol(glfw_SOURCES
         PROTOCOL
         "${WAYLAND_PROTOCOLS_PKGDATADIR}/unstable/relative-pointer/relative-pointer-unstable-v1.xml"