AppVeyor times out

[eschnett]

I have AppVeyor time out for #9898 when running on one core. The multi-core run did not time out. The build was stuck in osutils.jl -- this always takes a long time.

[staticfloat]

We are aware of appveyor issues. If you'd like us to restart a build for you, just comment on the issue in particular and we can deal with it there. (Perhaps there was another reason you opened this issue?)

[tkelman]

This may be related to the long-standing #7942, but I'm not positive.

Edit to add: I'm pretty sure I've seen this only on Win64 Julia, or at least far more often there. If we were running the tests in parallel then things would likely freeze and time out slightly more often.

[vtjnash]

closing since this is not exactly actionable

[tkelman]

I've raised this with Feodor and he's watched a few cases where a build had hung, but it was hard to tell whether anything was obviously wrong. Would be nice to fix this at some point, if anyone can figure out what's causing it.