Now, but that may change already in 6.1 in order to add CFI support.
We can bundle a newer version, but we don't need to require a newer
version. Simply conditional compile for the bits we need. If distro
slirp is too old, then sorry, you can't enable CFI + slirp at the
same time. If the distro really wants that combination we don't have
to own the solution - the distro should update their slirp.
Or to put it another way, QEMU doesn't need to go out of its way to
enable new features on old distros. We merely need to not regress
in the features we previously offered. We bundled slirp as a submodule
so that old distros didn't loose slirp entirely. We don't need to
offer CFI on those distros.