thanos: Synchronize go build tags with upstream

  subPackages = "cmd/thanos";

  # Verify in sync with https://github.com/thanos-io/thanos/blob/main/.promu.yml

  tags = [

    "netgo"

    "slicelabels"

  ];

  ldflags =

    let

      t = "github.com/prometheus/common/version";