Fuzzers: Avoid passing target backend as parameter

Changes various fuzz targets so that the target back-end language (HLSL,
MSL, SPIR-V or WGSL) is no longer passed as a command line argument, but
instead baked into the fuzzer's binary. This avoids a problem whereby a
ClusterFuzz bug reproducer does not use the required back-end command
line argument.

Change-Id: I64402a23391ca0f24c9d1ffd2aa2f218cc7106b1
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/63163
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ryan Harrison <rharrison@chromium.org>
Commit-Queue: Alastair Donaldson <afdx@google.com>

fuzzers/tint_regex_fuzzer/fuzzer.cc

@@ -18,6 +18,7 @@
 
 #include "fuzzers/tint_common_fuzzer.h"
 #include "fuzzers/tint_regex_fuzzer/cli.h"
+#include "fuzzers/tint_regex_fuzzer/override_cli_params.h"
 #include "fuzzers/tint_regex_fuzzer/util.h"
 #include "fuzzers/tint_regex_fuzzer/wgsl_mutator.h"
 
@@ -44,6 +45,9 @@ extern "C" int LLVMFuzzerInitialize(int* argc, char*** argv) {
   // Parse CLI parameters. `ParseCliParams` will call `exit` if some parameter
   // is invalid.
   cli_params = ParseCliParams(argc, *argv);
+  // For some fuzz targets it is desirable to force the values of certain CLI
+  // parameters after parsing.
+  OverrideCliParams(cli_params);
   return 0;
 }