Fix for builds without the Swift Swift parser

Author: DougGregor

lib/Sema/TypeCheckMacros.cpp

@@ -98,9 +98,10 @@ static void const *lookupMacroTypeMetadataByExternalName(
 MacroDefinition MacroDefinitionRequest::evaluate(
     Evaluator &evaluator, MacroDecl *macro
 ) const {
-#if SWIFT_SWIFT_PARSER
   ASTContext &ctx = macro->getASTContext();
 
+#if SWIFT_SWIFT_PARSER
+
   /// Look for the type metadata given the external module and type names.
   auto macroMetatype = lookupMacroTypeMetadataByExternalName(
       ctx, macro->externalModuleName.str(),