This is mostly intended for Linux, where we are returning the OS version
in the PlatformVersion field, which seems reasonable. Often it is still
useful to know which Linux kernel is running.
For FreeBSD and Darwin the kernel version matches the platform version,
since they previously used the kernel version for the platform version.
For Windows the kernel version is empty, since there is no clear way
to determine it.
On supported hosts the value returned is a UUID (case preserving
from the value of the underlying OS).
For Linux this is generated once, randomly per boot. For FreeBSD and
Darwin this is a more durable value that should persist across reboots.
Lukas Fittl