[libFuzzer] Fix close_fd_mask.

[mpividori]

Summary

For Windows, sanitizers work with Handles, not with posix file descriptors, because they use the windows-specific API. So we need to convert the fds to handles before passing them to the sanitizer library.
After this change, close_fd_mask is fixed for Windows (this fix some tests too).

[mpividori]

@zturner You are right. Done.
Thanks.

lib/Fuzzer/FuzzerIO.h

 int CloseFile(int Fd);
 
 int DuplicateFile(int Fd);
 
 void RemoveFile(const std::string &Path);
 
 void DiscardOutput(int Fd);
 
+int GetHandleFromFd(int fd);
+
 }  // namespace fuzzer
 
 #endif  // LLVM_FUZZER_IO_H

lib/Fuzzer/FuzzerIO.cpp

 
 void DupAndCloseStderr() {
   int OutputFd = DuplicateFile(2);
   if (OutputFd > 0) {
     FILE *NewOutputFile = OpenFile(OutputFd, "w");
     if (NewOutputFile) {
       OutputFile = NewOutputFile;
       if (EF->__sanitizer_set_report_fd)
-        EF->__sanitizer_set_report_fd(reinterpret_cast<void *>(OutputFd));
+        EF->__sanitizer_set_report_fd(reinterpret_cast<void *>(
+            GetHandleFromFd(OutputFd)));
       DiscardOutput(2);
     }
   }
 }
 
 void CloseStdout() {
   DiscardOutput(1);
 }

lib/Fuzzer/FuzzerIOPosix.cpp

 void DiscardOutput(int Fd) {
   FILE* Temp = fopen("/dev/null", "w");
   if (!Temp)
     return;
   dup2(fileno(Temp), Fd);
   fclose(Temp);
 }
 
+int GetHandleFromFd(int fd) {
+  return fd;
+}
+
 std::string DirName(const std::string &FileName) {
   char *Tmp = new char[FileName.size() + 1];
   memcpy(Tmp, FileName.c_str(), FileName.size() + 1);
   std::string Res = dirname(Tmp);
   delete [] Tmp;
   return Res;
 }
 

lib/Fuzzer/FuzzerIOWindows.cpp

 void DiscardOutput(int Fd) {
   FILE* Temp = fopen("nul", "w");
   if (!Temp)
     return;
   _dup2(_fileno(Temp), Fd);
   fclose(Temp);
 }
 
+int GetHandleFromFd(int fd) {
+  return _get_osfhandle(fd);
+}
+
 static bool IsSeparator(char C) {
   return C == '\\' || C == '/';
 }
 
 // Parse disk designators, like "C:\". If Relative == true, also accepts: "C:".
 // Returns number of characters considered if successful.
 static size_t ParseDrive(const std::string &FileName, const size_t Offset,
                          bool Relative = true) {