message: Reinstate UNSUPPORTED: linux on stop-hook-threads.test
  This stanza was removed in r355213, but it seems that patch did not
  fully fix the problem, as the test still fails sporadically
  (particularly under heavy load) on linux.
diff: # RUN: %lldb -b -s %p/Inputs/stop-hook-threads-2.lldbinit -s %s -f %t \
  # RUN: | FileCheck --check-prefix=CHECK --check-prefix=CHECK-FILTER %s
  # XFAIL: system-windows
  +# UNSUPPORTED: system-linux
  thread list
  break set -f stop-hook-threads.cpp -p "Set break point at this line"
  