Support options --version and/or --help to run without DISPLAY

[umarcor]

As commented in #3, container images including irsim were added to hdl/containers. Before updating the images, we run some quick tests on them to ensure that the tools were successfully built/installed. Typically, we execute TOOL --version, TOOL -v, TOOL --help... That reveals issues with missing depencies and such.

It seems that irsim does not support options "version" or "help". Moreover, it fails if executed without DISPLAY:

https://github.com/hdl/containers/runs/6540621331?check_suite_focus=true#step:3:1468

  application-specific initialization failed: no display name and no $DISPLAY environment variable
  Error in startup script: no display name and no $DISPLAY environment variable

As a result, we are currently testing that /usr/local/bin/irsim exists, but we are not doing further tests in CI (https://github.com/hdl/containers/blob/main/test/irsim.sh#L26).

@RTimothyEdwards would it be possible to support irsim --version or irsim --help exiting cleanly despite DISPLAY not being available?

/cc @mithro