Merge the fuzzers used by oss-fuzz and internal fuzzers

Summary:
Add a time limit to the execution runtime of JS code, to prevent infinite loops
in generated JS being reported as timeouts in Hermes.

Reviewed By: neildhar

Differential Revision: D21726590

fbshipit-source-id: c99c41309807294a7af50e4891605eac843cda3f

tools/fuzzers/fuzzer-jsi-entry.cpp

@@ -30,6 +30,9 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
   std::string s(reinterpret_cast<const char *>(data), size);
   s.append("\0");
   auto runtime = makeHermesRuntime();
+  // Cap the run-time of the code so that fuzzing can stay efficient.
+  constexpr uint32_t kTimeoutForRunningInMs = 10000;
+  runtime->watchTimeLimit(kTimeoutForRunningInMs);
 
   try {
     runtime->evaluateJavaScript(std::make_unique<StringBuffer>(s), "");