[libFuzzer] Avoid STL in MSan test.

[morehouse]

Summary

STL can cause MSan false positives if lib[std]c++ isn't instrumented with MSan

[kcc]

err... partially taking my word back.. I do want to keep this test to use STL.
Instead of this change, please create another test, e.g. SimpleTestStdio.cpp, that won't use STL, and use the new test in msan runs.

[morehouse]

• Revert "[libFuzzer] Avoid std::cout in SimpleTest."
• Create SimpleTestStdio.cpp without STL.

[kcc]

LGTM

compiler-rt/test/fuzzer/SimpleTest.cpp

 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 
 // Simple test for a fuzzer. The fuzzer must find the string "Hi!".
 #include <assert.h>
-#include <cstddef>
 #include <cstdint>
+#include <cstdio>
 #include <cstdlib>
-#include <iostream>
-#include <ostream>
 
 static volatile int Sink;
 
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
   assert(Data);
   if (Size > 0 && Data[0] == 'H') {
     Sink = 1;
     if (Size > 1 && Data[1] == 'i') {
       Sink = 2;
       if (Size > 2 && Data[2] == '!') {
-        std::cout << "BINGO; Found the target, exiting\n" << std::flush;
+        printf("BINGO; Found the target, exiting\n");
+        fflush(stdout);
         exit(0);
       }
     }
   }
   return 0;
 }