Fixes a few more places where we were manually setting the filename.

llvm-svn: 216247
diff --git a/lldb/source/Expression/ClangExpressionParser.cpp b/lldb/source/Expression/ClangExpressionParser.cpp
index 4d49619..3b0269a 100644
--- a/lldb/source/Expression/ClangExpressionParser.cpp
+++ b/lldb/source/Expression/ClangExpressionParser.cpp
@@ -312,7 +312,7 @@
         FileSpec tmpdir_file_spec;
         if (HostInfo::GetLLDBPath(lldb::ePathTypeLLDBTempSystemDir, tmpdir_file_spec))
         {
-            tmpdir_file_spec.GetFilename().SetCString("expr.XXXXXX");
+            tmpdir_file_spec.AppendPathComponent("expr.XXXXXX");
             temp_source_path = std::move(tmpdir_file_spec.GetPath());
         }
         else