MAINT: Use better detection for the lua libraries.
MAINT: Use better detection for the lua libraries.

Changed to use the $(shell ...) GNU makefile construct as this is safer
and can be guaranteed to only be run once. Also check correctly for the
version (if any) of lua we support. We could be checking for later versions
if required.

Change-Id: I4fdebf8fe705e30e91ec6ab50dd85c426106ab08
Reviewed-by: Scott Parlane <85029adc3fa41ef14594a57826619713bfe95f25@alliedtelesis.co.nz>
Reviewed-by: Ridge Kennedy <c60c433c4c1ae237d133641099200771ff6f6f30@alliedtelesis.co.nz>
Signed-off-by: Scott Parlane <85029adc3fa41ef14594a57826619713bfe95f25@alliedtelesis.co.nz>

ATL-NZ/buildsyspp,alliedtelesis/buildsyspp