[gn build] Port 8a65c4f

Author: aeubanks

llvm/utils/gn/secondary/libcxx/include/BUILD.gn

@@ -1528,6 +1528,7 @@ if (current_toolchain == default_toolchain) {
       "__type_traits/is_trivially_relocatable.h",
       "__type_traits/is_unbounded_array.h",
       "__type_traits/is_union.h",
+      "__type_traits/is_unqualified.h",
       "__type_traits/is_unsigned.h",
       "__type_traits/is_valid_expansion.h",
       "__type_traits/is_void.h",