[libclang] When there's a file error when saving the PCH, make sure to

clear the error from raw_fd_ostream, otherwise we will crash.

rdar://10976410

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@152605 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Frontend/ASTUnit.cpp

@@ -2411,8 +2411,10 @@ CXSaveError ASTUnit::Save(StringRef File) {
 
   serialize(Out);
   Out.close();
-  if (Out.has_error())
+  if (Out.has_error()) {
+    Out.clear_error();
     return CXSaveError_Unknown;
+  }
 
   if (llvm::sys::fs::rename(TempPath.str(), File)) {
     bool exists;