Follow up on D69112, fix build break for skipping field initialization

Clang emit warning for skipping field initialization. Add {} to fix it.
This is a patch that fixes issue introduced in https://reviews.llvm.org/D69112

Author: jasonliudev

llvm/lib/MC/XCOFFObjectWriter.cpp

@@ -156,8 +156,8 @@ class XCOFFObjectWriter : public MCObjectWriter {
   // CsectGroups. These store the csects which make up different parts of
   // the sections. Should have one for each set of csects that get mapped into
   // the same section and get handled in a 'similar' way.
-  CsectGroup ProgramCodeCsects{CsectGroup::LabelDefSupported};
-  CsectGroup BSSCsects{CsectGroup::LabelDefUnsupported};
+  CsectGroup ProgramCodeCsects{CsectGroup::LabelDefSupported, {}};
+  CsectGroup BSSCsects{CsectGroup::LabelDefUnsupported, {}};
 
   // The Predefined sections.
   Section Text;