linux-info.eclass: linux-info_get_any_version, die on failure

Make linux-info_get_any_version die if it can't determine any version
of the Linux kernel. This indicates a problem with the eclass code
(as it should not happen on Linux) and the missing KV_* variables
are going to cause random misbehavior and failures.

eclass/linux-info.eclass

@@ -630,7 +630,9 @@ get_running_version() {
 linux-info_get_any_version() {
  if ! get_version; then
  ewarn "Unable to calculate Linux Kernel version for build, attempting to use running version"
- get_running_version
+ if ! get_running_version; then
+ die "Unable to determine any Linux Kernel version, please report a bug"
+ fi
  fi
 }