GN files, initial check in

First version of Chromium build files for SwiftShader.
Works for Linux only at this point.
Other platforms are there, but untested at the moment.

Change-Id: I8f389db9937feda74c7009cf7a22938dab9e69d5
Reviewed-on: https://swiftshader-review.googlesource.com/5520
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <capn@google.com>

src/Main/BUILD.gn

diff --git a/src/Main/BUILD.gn b/src/Main/BUILD.gn
new file mode 100644
index 0000000..254256f
--- /dev/null
+++ b/src/Main/BUILD.gn
@@ -0,0 +1,68 @@
+# Copyright 2016 The SwiftShader Authors. All Rights Reserved.
+#
+# 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.
+
+# Need a separate config to ensure the warnings are added to the end.
+config("swiftshader_main_private_config") {
+  if (is_clang) {
+    cflags = [
+      "-DLOG_TAG=\"swiftshader_main\"",
+      "-msse2",
+    ]
+
+    if (!is_debug) {
+      cflags += [
+        "-DNDEBUG",
+        "-DANGLE_DISABLE_TRACE",
+      ]
+    }
+  }
+}
+
+source_set("swiftshader_main") {
+  deps = [
+    "../Common:swiftshader_common",
+  ]
+
+  sources = [
+    "Config.cpp",
+    "FrameBuffer.cpp",
+    "SwiftConfig.cpp",
+  ]
+
+  if (host_os == "linux") {
+    sources += [
+      "libX11.cpp",
+      "FrameBufferX11.cpp",
+    ]
+  } else if (host_os == "mac") {
+    sources += [
+      "FrameBufferOSX.mm",
+    ]
+  } else if (host_os == "win") {
+    sources += [
+      "FrameBufferDD.cpp",
+      "FrameBufferGDI.cpp",
+      "FrameBufferWin.cpp",
+    ]
+  }
+
+  configs += [
+    ":swiftshader_main_private_config",
+  ]
+
+  include_dirs = [
+    "..",
+    "../Common",
+  ]
+}
\ No newline at end of file