Improve: IPAddress.ipv6_to_bytes Musl Platform support

[636f7374]

Summary

• Added support for Musl IPv6.
  • maxminddb.cr/src/maxminddb/ip_address.cr#L38

Solution

    {% if flag?(:darwin) || flag?(:openbsd) || flag?(:freebsd) %}
      ipv6_address = pointer.value.sin6_addr.__u6_addr.__u6_addr8
      memory.write ipv6_address.to_slice
    {% elsif flag?(:linux) && flag?(:musl) %}
      ipv6_address = pointer.value.sin6_addr.__in6_union.__s6_addr
      memory.write ipv6_address.to_slice
    {% elsif flag?(:linux) %}
      ipv6_address = pointer.value.sin6_addr.__in6_u.__u6_addr8
      memory.write ipv6_address.to_slice
    {% else %}
      return
    {% end %}

[636f7374]

If needed.