Add incrementalExternalDepend as an Incremental NodeKind

unittests/Driver/UnitTestSourceFileDepGraphFactory.cpp

@@ -147,6 +147,7 @@ UnitTestSourceFileDepGraphFactory::singleNameIsContext(const NodeKind kind) {
     return true;
   case NodeKind::topLevel:
   case NodeKind::dynamicLookup:
+  case NodeKind::incrementalExternalDepend:
   case NodeKind::externalDepend:
   case NodeKind::sourceFileProvide:
     return false;