Attempt to make tests pass on FreeBSD

[JamesWrigley]

With luck this will fix some failures I saw on freebsd: https://buildkite.com/julialang/julia-master/builds/38343#0190dc42-ca45-4f4c-a6bd-b3d380d210dd/717-1489

Test Failed at /usr/home/julia/.buildkite-agent/builds/freebsd13-amdci6-2/julialang/julia-master/julia-35e0d9cefc/share/julia/stdlib/v1.12/Downloads/test/runtests.jl:354
  Expression: startswith(err.message, "Could not resolve host")
   Evaluated: startswith("Resolving timed out after 30005 milliseconds", "Could not resolve host")
Error in testset Downloads:
Test Failed at /usr/home/julia/.buildkite-agent/builds/freebsd13-amdci6-2/julialang/julia-master/julia-35e0d9cefc/share/julia/stdlib/v1.12/Downloads/test/runtests.jl:360
  Expression: startswith(err.message, "Could not resolve host")
   Evaluated: startswith("Resolving timed out after 30002 milliseconds", "Could not resolve host")

I think ideally the timeout would be a bit shorter than 30s but I'm not sure how to change that.

[JamesWrigley]

Hmm on second thoughts 'resolving timed out' and 'could not resolve' are quite different errors, so maybe it's better to just skip those tests on freebsd? Though it does seem best to fix the resolver on the freebsd machine in CI.