Use correct cmake version variable in pdal-config
Use correct cmake version variable in pdal-config

`pdal-config` didn't spit out the version with the old way.

[skip ci]

boundlessgeo/PDAL,mpgerlek/PDAL-old,DougFirErickson/PDAL,DougFirErickson/PDAL,lucadelu/PDAL,mpgerlek/PDAL-old,Sciumo/PDAL,Sciumo/PDAL,DougFirErickson/PDAL,lucadelu/PDAL,radiantbluetechnologies/PDAL,jwomeara/PDAL,Sciumo/PDAL,mtCarto/PDAL,mtCarto/PDAL,Sciumo/PDAL,radiantbluetechnologies/PDAL,jwomeara/PDAL,lucadelu/PDAL,DougFirErickson/PDAL,mpgerlek/PDAL-old,boundlessgeo/PDAL,boundlessgeo/PDAL,radiantbluetechnologies/PDAL,mtCarto/PDAL,jwomeara/PDAL,boundlessgeo/PDAL,lucadelu/PDAL,mtCarto/PDAL,radiantbluetechnologies/PDAL,jwomeara/PDAL,mpgerlek/PDAL-old