The test.json format currently has three keys related to skipping tests:
* `skip_on_jobname`
* `skip_on_os`
* `skip_on_env`
While `skip_on_env` marks the test itself as skipped, i.e. they don't get run when the
conditions are met, the other two skip options are just marking the test as "expected to be skipped"
if the conditions apply, i.e. they want to see `MESON_SKIP_TEST` in the output and things will
fail if that doesn't happen. They don't actually skip the tests as the names imply.
To make this clearer rename the keys:
* `skip_on_jobname` -> `expect_skip_on_jobname`
* `skip_on_os` -> `expect_skip_on_os`
`skip_on_env` stays the same, since that actually skips.
The docs were also confused about this, so adjust that too.
I guess the intent was that tests of thread/debug library variants only
get run with MSVC, but currently this test isn't getting run at all in
our Windows CI (since boost got removed from the VM image [1], and we
didn't notice, more on which anon).
[1] https://github.com/actions/virtual-environments/pull/2843
Christoph Reiter