0.5.0 boringtun crate is broken

[jamesgecargo]

We install boringtun via a dockerfile like so:

FROM debian:latest

RUN apt-get update && \
    apt-get -y install ca-certificates curl build-essential && \
    curl https://sh.rustup.rs -sSf | sh -s -- -y && \
    ~/.cargo/bin/cargo install boringtun

This worked fine up until a day ago but now it fails with an error:

...
#5 62.71 error: there is nothing to install in `boringtun v0.5.0`, because it has no binaries
#5 62.71 `cargo install` is only for installing programs, and can't be used with libraries.
#5 62.71 To use a library crate, add it as a dependency in a Cargo project instead.

If we pass in --version 0.4.0 when installing boringtun then it starts working again.

Thus all signs point to version 0.5.0 of the boringtun crate being broken.

[Noah-Kennedy]

We split it into two crates. Install boringtun-cli for the binary.