Make host-emulate/meson.build compatible with Busybox
Make host-emulate/meson.build compatible with Busybox

Busybox only supports the short option '-k'. (#4866)

Using this instead of '--keep' allows fwupd to be built on systems like Alpine Linux where /bin/gzip is supplied by Busybox.
fwupd/fwupd,fwupd/fwupd,fwupd/fwupd,fwupd/fwupd