It looks that the musl library did not added this T_OPT define yet, all others (T_A, T_AAAA) are there: [link](https://git.musl-libc.org/cgit/musl/tree/include/arpa/nameser.h). I don't want to change the complete implementation just for a bug fix, this might have some other side-effects as well for other distributions and/or libraries.
Can you check if it works now with commit cec1043a9c