external/test: make stripping out version number more robust
external/test: make stripping out version number more robust

For some bizarre reason, Travis started failing on this
substitution when there'd been zero code changes in this
area... This at least papers over whatever the problem is
for the time being.

Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

qemu/skiboot,stewart-ibm/skiboot,shenki/skiboot,qemu/skiboot,legoater/skiboot,open-power/skiboot,legoater/skiboot,legoater/skiboot,shenki/skiboot,open-power/skiboot,stewart-ibm/skiboot,shenki/skiboot,shenki/skiboot,open-power/skiboot,shenki/skiboot,legoater/skiboot,qemu/skiboot,qemu/skiboot,open-power/skiboot,qemu/skiboot,stewart-ibm/skiboot,legoater/skiboot,open-power/skiboot