com.docker.slirp.exe: link against {lwt,uwt}.preemptive
com.docker.slirp.exe: link against {lwt,uwt}.preemptive

Although these are referenced in the hostnet library they aren't used
and so probably aren't really included, but they are needed.

Signed-off-by: David Scott <63c9eb0ea83039690fefa11afe17873ba8278a56@docker.com>

djs55/vpnkit,djs55/vpnkit,djs55/vpnkit