[Support] Don't return an error if realPath fails.

In openFileForRead, we would not previously return an error
if real_path resolution failed.  After a recent patch, we
started propagating this error up.  This caused a failure
in clang when trying to call openFileForRead("nul").  This
patch restores the previous behavior of not propagating this
error up.

llvm-svn: 297488
diff --git a/llvm/lib/Support/Windows/Path.inc b/llvm/lib/Support/Windows/Path.inc
index c758289..d8a14b4 100644
--- a/llvm/lib/Support/Windows/Path.inc
+++ b/llvm/lib/Support/Windows/Path.inc
@@ -857,12 +857,11 @@
   }
 
   // Fetch the real name of the file, if the user asked
-  std::error_code EC;
   if (RealPath)
-    EC = realPathFromHandle(H, *RealPath);
+    realPathFromHandle(H, *RealPath);
 
   ResultFD = FD;
-  return EC;
+  return std::error_code();
 }
 
 std::error_code openFileForWrite(const Twine &Name, int &ResultFD,