add type, causes ambiguous error on linux

Author: bhoehl

ift/feature_registry/registry_to_cc.py

@@ -44,7 +44,7 @@ def print_set():
 print("namespace ift::feature_registry {")
 print("")
 print("static const absl::flat_hash_set<hb_tag_t>& DefaultFeatureTags() {")
-print("  static const absl::NoDestructor<absl::flat_hash_set<hb_tag_t>> kDefaultFeatures({")
+print("  static const absl::NoDestructor<absl::flat_hash_set<hb_tag_t>> kDefaultFeatures((absl::flat_hash_set<hb_tag_t>) {")
 print_set()
 print("  });")
 print("  return *kDefaultFeatures;")