Revert "Use upstream SPIRV-Cross GN files."

This reverts commit 9fdbb74072.

Reason for revert: The SPIRV-Cross GN files have a bug which is fixed upstream, but Skia is on an old version of SPIRV-Cross so they don't have the fix. So, the build fails when rolling Dawn into Skia complaining about unknown `-fno-exceptions` on the windows bots. Need Skia to either move to vulkan-deps, or roll their spirv-cross forward before this can re-land.

Original change's description:
> Use upstream SPIRV-Cross GN files.
>
> Previously spirv-cross didn't have its own sources files but this
> changed recently so we should use them. This will ultimately allow
> sharing targets between multiple components in Chromium.
>
> Bug: chromium:1179277
> Change-Id: Ib4bb1884b9ba9c4c3804e96d8adbb8905c60c9a3
> Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/41725
> Auto-Submit: Corentin Wallez <cwallez@chromium.org>
> Reviewed-by: Peng Huang <penghuang@chromium.org>
> Reviewed-by: Austin Eng <enga@chromium.org>
> Commit-Queue: Corentin Wallez <cwallez@chromium.org>

Bug: chromium:1179277
Change-Id: If1003bafa7b35f502c08b2dab91dd3d416aab077
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/42420
Commit-Queue: dan sinclair <dsinclair@chromium.org>
Commit-Queue: Austin Eng <enga@chromium.org>
Auto-Submit: dan sinclair <dsinclair@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>

src/dawn_native/BUILD.gn

@@ -143,7 +143,7 @@ source_set("dawn_native_sources") {
     ":dawn_native_headers",
     ":dawn_native_utils_gen",
     "${dawn_root}/src/common",
-    "${dawn_spirv_cross_dir}/gn:spirv_cross_sources",
+    "${dawn_root}/third_party/gn/spirv_cross:spirv_cross",
     "${dawn_spirv_tools_dir}:spvtools_opt",
     "${dawn_spirv_tools_dir}:spvtools_val",
   ]

third_party/gn/spirv_cross/BUILD.gn

@@ -0,0 +1,70 @@
+# 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.
+
+import("../../../scripts/dawn_overrides_with_defaults.gni")
+
+import("//build_overrides/build.gni")
+
+# SPIRV_Cross does not have BUILD.gn rules, so implement our own.
+is_msvc = is_win && !is_clang
+
+config("spirv_cross_public") {
+  include_dirs = [
+    "${dawn_spirv_cross_dir}",
+    "${dawn_spirv_cross_dir}/..",
+  ]
+  defines = [ "SPIRV_CROSS_EXCEPTIONS_TO_ASSERTIONS" ]
+}
+
+config("spirv_cross_internal") {
+  if (!is_msvc) {
+    cflags_cc = [
+      "-Wno-implicit-fallthrough",
+      "-Wno-return-type",
+      "-Wno-sign-compare",
+    ]
+  } else {
+    # Disable "not all control paths return a value" warning.
+    cflags_cc = [ "/wd4715" ]
+  }
+}
+
+source_set("spirv_cross") {
+  public_configs = [ ":spirv_cross_public" ]
+  configs += [ ":spirv_cross_internal" ]
+
+  sources = [
+    "${dawn_spirv_cross_dir}/GLSL.std.450.h",
+    "${dawn_spirv_cross_dir}/spirv.hpp",
+    "${dawn_spirv_cross_dir}/spirv_cfg.cpp",
+    "${dawn_spirv_cross_dir}/spirv_cfg.hpp",
+    "${dawn_spirv_cross_dir}/spirv_common.hpp",
+    "${dawn_spirv_cross_dir}/spirv_cross.cpp",
+    "${dawn_spirv_cross_dir}/spirv_cross.hpp",
+    "${dawn_spirv_cross_dir}/spirv_cross_containers.hpp",
+    "${dawn_spirv_cross_dir}/spirv_cross_error_handling.hpp",
+    "${dawn_spirv_cross_dir}/spirv_cross_parsed_ir.cpp",
+    "${dawn_spirv_cross_dir}/spirv_cross_parsed_ir.hpp",
+    "${dawn_spirv_cross_dir}/spirv_glsl.cpp",
+    "${dawn_spirv_cross_dir}/spirv_glsl.hpp",
+    "${dawn_spirv_cross_dir}/spirv_hlsl.cpp",
+    "${dawn_spirv_cross_dir}/spirv_hlsl.hpp",
+    "${dawn_spirv_cross_dir}/spirv_msl.cpp",
+    "${dawn_spirv_cross_dir}/spirv_msl.hpp",
+    "${dawn_spirv_cross_dir}/spirv_parser.cpp",
+    "${dawn_spirv_cross_dir}/spirv_parser.hpp",
+    "${dawn_spirv_cross_dir}/spirv_reflect.cpp",
+    "${dawn_spirv_cross_dir}/spirv_reflect.hpp",
+  ]
+}