this commit adds support for Gitpod.io, a free automated
dev environment that makes contributing and generally working on GitHub
projects much easier. It allows anyone to start a ready-to-code dev
environment for any branch, issue and pull request with a single click.
Based on os.phil-opp.com ideas it includes running test framework in
qemu semihosting mode so that tests can indicate pass or fail to calling
process.
GitHub Actions are configured to run these tests and validate acceptance.
Add test-runner target to perform tests in qemu.
Add -nographic for qemu running tests.
Drop serial for qemu tests as well.
Berkus Decker