Adjust the workaround in the previous commit.  pthread_sigmask() doesn't quite seem to work, but sigprocmask() seems to.  (why?)
Adjust the workaround in the previous commit.  pthread_sigmask()
doesn't quite seem to work, but sigprocmask() seems to.  (why?)

HPCToolkit/hpctoolkit,zcth428/hpctoolkit,HPCToolkit/hpctoolkit,zcth428/hpctoolkit111,zcth428/hpctoolkit111,HPCToolkit/hpctoolkit,zcth428/hpctoolkit111,zcth428/hpctoolkit111,zcth428/hpctoolkit,zcth428/hpctoolkit,zcth428/hpctoolkit,HPCToolkit/hpctoolkit,HPCToolkit/hpctoolkit,zcth428/hpctoolkit111,HPCToolkit/hpctoolkit,zcth428/hpctoolkit