switch to meson build + refactor code to remove compile warning

seat.c

@@ -10,6 +10,7 @@
 
 static void configure_keyboard(struct diyac_seat* seat, struct diyac_input* input, bool force)
 {
+    (void) seat;
     struct wlr_input_device *device = input->device;
     assert(device->type == WLR_INPUT_DEVICE_KEYBOARD);
     struct diyac_keyboard *keyboard = (struct diyac_keyboard *)input;
@@ -41,6 +42,7 @@ static void configure_keyboard(struct diyac_seat* seat, struct diyac_input* inpu
 static void keyboard_handle_modifiers(
     struct wl_listener *listener, void *data)
 {
+    (void) data;
     /* This event is raised when a modifier key, such as shift or alt, is
      * pressed. We simply communicate this to the client. */
     struct diyac_keyboard *keyboard =
@@ -128,6 +130,7 @@ static void keyboard_handle_key(
 
 static void input_handle_destroy(struct wl_listener *listener, void *data)
 {
+    (void) data;
     /* This event is raised by the keyboard base wlr_input_device to signal
      * the destruction of the wlr_keyboard. It will no longer receive events
      * and should be destroyed.