[libFuzzer] fix clang-tidy

[libFuzzer] fix clang-tidy

Reviewed By: morehouse

Differential Revision: https://reviews.llvm.org/D107382

GitOrigin-RevId: ff163ef12b3093c14b1261f7f5a31c52cac9320a
diff --git a/FuzzerMerge.h b/FuzzerMerge.h
index d3d28b9..de21301 100644
--- a/FuzzerMerge.h
+++ b/FuzzerMerge.h
@@ -41,6 +41,7 @@
 #define LLVM_FUZZER_MERGE_H
 
 #include "FuzzerDefs.h"
+#include "FuzzerIO.h"
 
 #include <istream>
 #include <ostream>