[libFuzzer] include FuzzerIO.h and hopefully fix the Mac build. reported by Dejan Mircevski

llvm-svn: 288979
diff --git a/llvm/lib/Fuzzer/FuzzerExtFunctionsDlsym.cpp b/llvm/lib/Fuzzer/FuzzerExtFunctionsDlsym.cpp
index 78d8de7..65b0458 100644
--- a/llvm/lib/Fuzzer/FuzzerExtFunctionsDlsym.cpp
+++ b/llvm/lib/Fuzzer/FuzzerExtFunctionsDlsym.cpp
@@ -15,6 +15,7 @@
 #if LIBFUZZER_APPLE
 
 #include "FuzzerExtFunctions.h"
+#include "FuzzerIO.h"
 #include <dlfcn.h>
 
 using namespace fuzzer;