Add '-tint_dump_input=true/false' to fuzzers to dump input spv/wgsl to a file

When enabled, the input spv/wgsl is dumped to a file named
"fuzzer_input_<hash of file>.spv/wgsl".

Note that this adds the setting to all the fuzzers in the root of
fuzzers/, but not to tint_ast_fuzzer, tint_regex_fuzzer, nor
tint_spirv_tools_fuzzer as they currently to their own CLI parsing.

Change-Id: I268ffd842b94be1cbb78eb199d5662712ff71053
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/61000
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: Antonio Maiorano <amaiorano@google.com>

fuzzers/cli.h

@@ -0,0 +1,43 @@
+// Copyright 2021 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.
+
+#ifndef FUZZERS_CLI_H_
+#define FUZZERS_CLI_H_
+
+#include <cstdint>
+
+namespace tint {
+namespace fuzzers {
+
+/// CLI parameters accepted by the fuzzer. Type -tint_help in the CLI to see the
+/// help message
+struct CliParams {
+  bool dump_input = false;
+};
+
+/// @brief Parses CLI parameters.
+///
+/// This function will exit the process with non-zero return code if some
+/// parameters are invalid. This function will remove recognized parameters from
+/// `argv` and adjust `argc` accordingly.
+///
+/// @param argc - the total number of parameters.
+/// @param argv - array of all CLI parameters.
+/// @return parsed parameters.
+CliParams ParseCliParams(int* argc, char** argv);
+
+}  // namespace fuzzers
+}  // namespace tint
+
+#endif  // FUZZERS_CLI_H_