Binders is a low level affinity layer for precise control over where workers and
shepherds are allocated. It is implemented as a colon-seperated list of
cpustrings, where each cpustring is a shepherd. It is controlled by the
environment variable QT_CPUBIND.

Example usages:

  Two shepherds, first has workers on cpus 0-3, second has workers on cpus 4-7.
  QT_CPUBIND=0-3:4-7

  One shepherd, workers on cpus 0,4,8,12
  QT_CPUBIND=0,4,8,12
