Toolbx: Add host-spawn.

toolbx/Dockerfile

+FROM docker.io/golang:1.20 as golang
+RUN go install github.com/1player/host-spawn@1.4.1
+
 FROM docker.io/debian:testing-backports
+COPY --from=golang /go/bin/host-spawn /usr/local/bin/host-spawn
 SHELL ["/bin/bash", "-o", "pipefail", "-xc"]
 ADD [ "https://www.shore.co.il/blog/static/runas", "/usr/local/sbin/runas" ]
 # hadolint ignore=DL3008