Add in basic BUILD.gn and additional DEPS

This is a minimal config that gets us building the tint binary from samples/

BUG=tint:2

Change-Id: Ifafa903e99a34f1c47177eb954df69ecbe70cb36
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/19106
Reviewed-by: dan sinclair <dsinclair@google.com>

build_overrides/build.gni

@@ -0,0 +1,48 @@
+# Copyright 2020 The Tint 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.
+
+# This file contains build-related overrides.
+
+# Variable that can be used to support multiple build scenarios, like having
+# Chromium specific targets in a client project's GN file etc.
+build_with_chromium = false
+
+# Builds don't use Chromium's third_party/binutils.
+linux_use_bundled_binutils_override = false
+
+declare_args() {
+  # Android 32-bit non-component, non-clang builds cannot have symbol_level=2
+  # due to 4GiB file size limit, see https://crbug.com/648948.
+  # Set this flag to true to skip the assertion.
+  ignore_elf32_limitations = false
+
+  # Use the system install of Xcode for tools like ibtool, libtool, etc.
+  # This does not affect the compiler. When this variable is false, targets will
+  # instead use a hermetic install of Xcode. [The hermetic install can be
+  # obtained with gclient sync after setting the environment variable
+  # FORCE_MAC_TOOLCHAIN].
+  use_system_xcode = ""
+}
+
+if (use_system_xcode == "") {
+  if (target_os == "mac") {
+    _result = exec_script("//build/mac/should_use_hermetic_xcode.py",
+                          [ target_os ],
+                          "value")
+    use_system_xcode = _result == 0
+  }
+  if (target_os == "ios") {
+    use_system_xcode = true
+  }
+}

build_overrides/tint.gni

@@ -0,0 +1,15 @@
+# Copyright 2020 The Tint 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.
+
+# This file contains Tint-related overrides.