There is no way to stop a background task simply and safely with
cmd.exe, but in appveyor.yml we can use PowerShell, so use its job
support to do it instead.
This is important because AppVeyor waits until all jobs launched by the
script terminate, so without stopping the background job all builds
waited for an hour before timing out.
Don't use quotes around the value, they're not special for cmd.exe
and remain part of the actual variable value.
Co-authored-by: Maarten <MaartenBent@users.noreply.github.com>
Run httpbin (either directly or inside a container) and set
WX_TEST_WEBREQUEST_URL to point to localhost.
Note that it is important _not_ to have a trailing slash in the root
URL, otherwise WebRequest::Auth::Digest test would fail.
