[libFuzzer] do mutations based on memcmp/strcmp interceptors under a separate flag (-use_memcmp, default=1)

llvm-svn: 257873
diff --git a/llvm/lib/Fuzzer/FuzzerInternal.h b/llvm/lib/Fuzzer/FuzzerInternal.h
index 7d4de95..6c16b76 100644
--- a/llvm/lib/Fuzzer/FuzzerInternal.h
+++ b/llvm/lib/Fuzzer/FuzzerInternal.h
@@ -83,6 +83,7 @@
     bool UseCounters = false;
     bool UseIndirCalls = true;
     bool UseTraces = false;
+    bool UseMemcmp = true;
     bool UseFullCoverageSet  = false;
     bool Reload = true;
     bool ShuffleAtStartUp = true;