/var/lib/tox-bootstrapd on the host is owned by hosts's tox-bootstrapd
and chowned 700, but the container attempts to access it as its own
tox-bootstrapd user with possibly different uid:gid, which will fail if
host's tox-bootstrapd user has different uid:gid than the tox-bootstrapd
user inside the container.
This change makes the container use host's tox-bootstrapd uid:gid, which
fixes the issue.
* Use fully static build for the bootstrap daemon.
* Store a sha256sum of the binary in the repo.
* Updated documentation for it.
* Add support for fully static build in cmake.
* Enable the docker build on every PR, so we catch changes to the
checksum. I realise this is adding toil, but having the checksum is
valuable for security of released binaries.
tox-bootstrapd can use around 600 TCP sockets during TCP server's normal
functioning. Many systems default to having a soft limit of 1024 open file
descriptors, which we are close to reaching, so it was suggested we bump that
limit to a higher number. iphy suggested increasing it to 32768.
