Fix by Donn Cave for BeOS (SF #403642):

Fix by Donn Cave for BeOS (SF #403642):

  UNIX style fork/execve/wait are not fully compatible with thread
  support on BeOS.  For Python, that means neither fork() from import
  nor import from a fork work reliably. os._execvpe() does the latter,
  importing tempfile to set up a tantalizing target for hackers. This
  patch replaces both the tempfile name generation and the exec that
  uses it, in case we're on BeOS. Need this for
  setup:distutils:execvp(); symptoms are random crashes and internal
  BeOS error messages about th name, in case we're on BeOS. It's an
  issue because setup.py + distutils calls os.execvp(); symptoms are
  random crashes during setup.py, and internal BeOS error messages
  about thread IDs.