MB-53204: Add workaround for Win32 CV failures
MB-53204: Add workaround for Win32 CV failures

The unit test used std::filesystem::remove_all to remove a
directory to "resume" its child processes. Unfortunately
that function doesn't work properly on older versions of
windows.

See: https://developercommunity.visualstudio.com/t/stdfilesystemremove-doesnt-work-under-windows-10-1/398243

and would fail with something like:

12:38:35 unknown file: error: C++ exception with description "remove_all: Incorrect function.: "C:/Jenkins/workspace/sigar-gerrit-master/sub_workspace/build/sigar/src/sigar_tests963101"" thrown in the test body.

We don't support such old versions, but we do at least have
one build slave which is running Windows 1607.

To work around the problem use cb::io::rmrf instead

Change-Id: I2eacc1fed592e6d7f399b60b166114dac3fad69c
Reviewed-on: https://review.couchbase.org/c/sigar/+/178263
Tested-by: Trond Norbye <60edd2ef23891a753f231b0c6f161dc634079a93@couchbase.com>
Tested-by: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Richard de Mellow <3b8534f7ae49c77465cd6f1b512f27ec39f3eddd@couchbase.com>

couchbase/sigar,couchbase/sigar