Add initial CMakeLists.txt files

Adds CMake support for:
 - Generating the Dawn headers and C++ wrappers
 - libdawn_wire
 - libdawn_native with the Metal backend for now
 - All the examples.

Bug: dawn:333

Change-Id: I6ffbe090b0bd21d6a805c03a507ad51fda0275ca
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/15720
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Dan Sinclair <dsinclair@chromium.org>

src/dawn_platform/CMakeLists.txt

@@ -0,0 +1,22 @@
+# Copyright 2020 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.
+
+add_library(dawn_platform STATIC ${DAWN_DUMMY_FILE})
+target_sources(dawn_platform PRIVATE
+    "${DAWN_INCLUDE_DIR}/dawn_platform/DawnPlatform.h"
+    "tracing/EventTracer.cpp"
+    "tracing/EventTracer.h"
+    "tracing/TraceEvent.h"
+)
+target_link_libraries(dawn_platform PRIVATE dawn_internal_config dawn_common)