Running some sub-tests in process groups causes tests to hang - the reason is
not yet known.
Disable the use of process groups for now.

This patch comes from OmniOS.

--- Python-3.14.0/Lib/test/libregrtest/worker.py.orig
+++ Python-3.14.0/Lib/test/libregrtest/worker.py
@@ -13,7 +13,8 @@
     get_temp_dir, get_work_dir, exit_timeout)
 
 
-USE_PROCESS_GROUP = (hasattr(os, "setsid") and hasattr(os, "killpg"))
+USE_PROCESS_GROUP = (hasattr(os, "setsid") and hasattr(os, "killpg")
+    and not sys.platform.startswith("sunos"))
 NEED_TTY = {
     'test_ioctl',
 }