um: do not send SIGALRM to userspace in time-travel mode

um: do not send SIGALRM to userspace in time-travel mode

We send a SIGALRM to userspace processes to interrupt them. Really,
doing so is only needed if they are actually executing at the time (to
ensure we return to kernelspace). Unfortunately, we do not have that
information readily available. We can however be sure that this is never
the case when we are in time-travel mode with infinite CPU.

Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20250408074524.300153-1-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>