When running the same kernel in a VM as on the host system and the
kernel boot message from the VM appears on the log output, the run tool
assumes that the host machine has rebooted unexpectedly. With this
commit, an unexpected reboot is assumed only if the kernel boot message
appears at the beginning of a line. On base-hw, we enforce a line feed
at the beginning of the boot message as the SPIKE emulator log starts
with the first message of the kernel lacking a line feed.
Fixes#2041
