fix: make test suite run on Macs — radicle-ci-broker

Change the radenv.sh script to use tilde expansion instead of getent. Macs do not have a getent - that’s a tool that’s specific to glibc, so it’s mostly only available on Linux systems. But we don’t need that: Bash can do the expansion directly.

Signed-off-by: Lars Wirzenius liw@liw.fi

 homedir="$(pwd)/homedir"
 CI_USER_HOME="$(getent passwd "$USER" | awk -F: '{ print $6 }')"
 env \
     PATH="$CI_USER_HOME/.radicle/bin:$PATH" \
     PATH=~/.radicle/bin:"$PATH" \
 	HOME="$homedir" \
 	RAD_PASSPHRASE=secret \
 	RAD_HOME="$homedir/.radicle" \

 The event synthesizer is a helper to feed the CI broker node events in
 a controlled fashion.
 ## We can run rad
 _Want:_ We can run rad.
 _Why:_ For many of the verification scenarios for the CI broker we
 need to run the Radicle `rad` command line tool. Depending on the
 environment we use for verification, `rad` may be installed in various
 places. Commonly, if installed using the Radicle installer, `rad` is
 installed into `~/.radicle/bin` and edits the shell initialization
 file to add that to `$PATH`. However, in a CI context, that
 initialization is not necessarily done and so the `radenv.sh` helper
 script adds that directory to the `$PATH` just in case. We verify in
 this scenario that we can run `rad` at all.
 _Who:_ `cib-devs`
 ~~~scenario
 given file radenv.sh
 when I run bash radenv.sh rad --version
 then command is successful
 ~~~
 ## Dummy adapter runs successfully
 _Want:_ The dummy adapter (in embedded file `dummy.sh`) runs