Build constraints must be added to every file. We only want to build
this package when the `integration` tag is set.
Without this, every build prints this warning:
# github.com/osbuild/osbuild-composer/cmd/osbuild-image-tests
runtime.main_main·f: function main is undeclared in the main package
When using %#v instead of %v, printing an error gives a slightly more
informative error message, therefore this commit switches to %#v in all
error prints.
This commit makes the osbuild-image-tests binary doing the same set of tests
like the old test/run script.
Changes from test/run:
- qemu/nspawn are now killed gracefully. Firstly, SIGTERM is sent.
If the process doesn't exit till the timeout, SIGKILL is sent.
I changed this because nspawn leaves some artifacts behind when killed
by SIGKILL.
- the unsharing of network namespace now works differently because of
systemd issue #15079
