Remove a given file even if openFileForRead fails.

[ruiu]

Summary

I think the constract of this function is to remove a file in some way,
whether in background or in foreground. This patch makes sure that it
removes a given file.

lld/trunk/ELF/Filesystem.cpp

if (!ThreadsEnabled || !sys::fs::exists(Path) ||
       !sys::fs::is_regular_file(Path))
     return;
 
   // We cannot just remove path from a different thread because we are now going
   // to create path as a new file.
   // Instead we open the file and unlink it on this thread. The unlink is fast
   // since the open fd guarantees that it is not removing the last reference.
   int FD;
-  if (sys::fs::openFileForRead(Path, FD))
-    return;
-
+  std::error_code EC = sys::fs::openFileForRead(Path, FD);
   sys::fs::remove(Path);
 
   // close and therefore remove TempPath in background.
+  if (!EC)
     std::thread([=] { ::close(FD); }).detach();
 #endif
 }
 
 // Simulate file creation to see if Path is writable.
 //
 // Determining whether a file is writable or not is amazingly hard,
 // and after all the only reliable way of doing that is to actually
 // create a file. But we don't want to do that in this function