[libFuzzer] allow passing 1 or more files as individual inputs

llvm-svn: 259459
diff --git a/llvm/lib/Fuzzer/FuzzerInternal.h b/llvm/lib/Fuzzer/FuzzerInternal.h
index d506f8f..07f45af 100644
--- a/llvm/lib/Fuzzer/FuzzerInternal.h
+++ b/llvm/lib/Fuzzer/FuzzerInternal.h
@@ -62,6 +62,7 @@
 
 typedef FixedWord<27> Word; // 28 bytes.
 
+bool IsFile(const std::string &Path);
 std::string FileToString(const std::string &Path);
 Unit FileToVector(const std::string &Path);
 void ReadDirToVectorOfUnits(const char *Path, std::vector<Unit> *V,