Update spirv-tools to get new code folding optimization.

This change includes a fix for an issue we filed against spirv-tools:
https://github.com/KhronosGroup/SPIRV-Tools/issues/4371

So, it should reduce the number of extraneous matrix copies in finalized
GLSL code.

I did quick size total of all filamat files (*) before and after this
update, it went from 11.3 MB to 11.1 MB.

(*) All backends are enabled, includes built-in Filament shaders and
gltfio ubershaders.

third_party/spirv-tools/test/diff/diff_test_utils.cpp

@@ -0,0 +1,58 @@
+// Copyright (c) 2022 Google LLC.
+//
+// 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.
+
+#include "diff_test_utils.h"
+
+#include "source/opt/build_module.h"
+#include "source/opt/ir_context.h"
+
+#include "spirv-tools/libspirv.hpp"
+#include "tools/io.h"
+#include "tools/util/cli_consumer.h"
+
+#include "gtest/gtest.h"
+
+namespace spvtools {
+namespace diff {
+
+static constexpr auto kDefaultEnvironment = SPV_ENV_UNIVERSAL_1_6;
+
+void DoStringDiffTest(const std::string& src_spirv,
+                      const std::string& dst_spirv,
+                      const std::string& expected_diff, Options options) {
+  // Load the src and dst modules
+  std::unique_ptr<spvtools::opt::IRContext> src = spvtools::BuildModule(
+      kDefaultEnvironment, spvtools::utils::CLIMessageConsumer, src_spirv,
+      spvtools::SpirvTools::kDefaultAssembleOption |
+          SPV_TEXT_TO_BINARY_OPTION_PRESERVE_NUMERIC_IDS);
+  ASSERT_TRUE(src);
+
+  std::unique_ptr<spvtools::opt::IRContext> dst = spvtools::BuildModule(
+      kDefaultEnvironment, spvtools::utils::CLIMessageConsumer, dst_spirv,
+      spvtools::SpirvTools::kDefaultAssembleOption |
+          SPV_TEXT_TO_BINARY_OPTION_PRESERVE_NUMERIC_IDS);
+  ASSERT_TRUE(dst);
+
+  // Take the diff
+  std::ostringstream diff_result;
+  spv_result_t result =
+      spvtools::diff::Diff(src.get(), dst.get(), diff_result, options);
+  ASSERT_EQ(result, SPV_SUCCESS);
+
+  // Expect they match
+  EXPECT_EQ(diff_result.str(), expected_diff);
+}
+
+}  // namespace diff
+}  // namespace spvtools