GN: Wayland build overrides

Introduce //build_overrides/wayland.gni to simplify the management of
the wayland dependencies.

Bug: chromium:1327041
Bug: angleproject:7409
Change-Id: Ib1e120c722aec6ff3cb171f39a8e794b93799129
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/93788
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: dan sinclair <dsinclair@google.com>
Reviewed-by: Ryan Harrison <rharrison@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>

build_overrides/wayland.gni

@@ -0,0 +1,19 @@
+# Copyright 2022 The Dawn Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import("//build/config/ozone.gni")
+
+# Dawn has no wayland third-party dir
+use_system_libwayland = true
+wayland_gn_dir = ""