runsc: Dup debug log file to stderr, so sentry panics don't get lost.
runsc: Dup debug log file to stderr, so sentry panics don't get lost.

Docker and containerd do not expose runsc's stderr, so tracking down sentry
panics can be painful.

If we have a debug log file, we should send panics (and all stderr data) to the
log file.

PiperOrigin-RevId: 215585559
Change-Id: I3844259ed0cd26e26422bcdb40dded302740b8b6

google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor