User mode networking with slirp on MacOs, setting host DNS server?

[Biff Eros]

Looking at this bug report:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=625689

There is this comment:

mjt@tls.msk.ru wrote:

> No the limitation isn't documented (yet), and it will be difficult
> to fix too, or maybe not worth a trouble really.  Two reasons.
> First of all, user-mode networking is not suitable for anything
> serious, you really want tap networking with bridges, which is
> about 100 times faster and actually works (e.g. ICMP).  Second,
> the implementation is rather simplistic - for DNS it merely
> forwards (like a NAT box) packets from guest to a nameserver
> from host /resolv.conf - only one nameserver, because you can't
> NAT to TWO destinations at once.  So in order to fix that,
> qemu has to become application-level proxy for DNS, instead
> of a simple NAT "device".

Unfortunately I'm on MacOs, and I don't want to be using resolv.conf.
I want it to use a locally running dnsmasq instead.  Can anyone point
me to which bit of source I need to change to hard-code this to
127.0.0.1, or is that out of the question?