[libFuzzer] fix a compiler warning

llvm-svn: 302747
diff --git a/llvm/lib/Fuzzer/FuzzerMutate.cpp b/llvm/lib/Fuzzer/FuzzerMutate.cpp
index cd846c7..a84e6ee 100644
--- a/llvm/lib/Fuzzer/FuzzerMutate.cpp
+++ b/llvm/lib/Fuzzer/FuzzerMutate.cpp
@@ -217,7 +217,8 @@
     size_t NumPositions = 0;
     for (const uint8_t *Cur = Data;
          Cur < End && NumPositions < kMaxNumPositions; Cur++) {
-      Cur = (uint8_t *)SearchMemory(Cur, End - Cur, ExistingBytes, ArgSize);
+      Cur =
+          (const uint8_t *)SearchMemory(Cur, End - Cur, ExistingBytes, ArgSize);
       if (!Cur) break;
       Positions[NumPositions++] = Cur - Data;
     }