Add package for lftp (#4634)
Add package for lftp (#4634)

* Add package for lftp

* Avoid expensive list processing

TheTimmy/spack,tmerrick1/spack,mfherbst/spack,iulian787/spack,lgarren/spack,iulian787/spack,lgarren/spack,LLNL/spack,krafczyk/spack,lgarren/spack,EmreAtes/spack,LLNL/spack,iulian787/spack,skosukhin/spack,skosukhin/spack,EmreAtes/spack,matthiasdiener/spack,tmerrick1/spack,krafczyk/spack,krafczyk/spack,LLNL/spack,tmerrick1/spack,krafczyk/spack,matthiasdiener/spack,lgarren/spack,EmreAtes/spack,matthiasdiener/spack,EmreAtes/spack,TheTimmy/spack,iulian787/spack,TheTimmy/spack,krafczyk/spack,TheTimmy/spack,LLNL/spack,lgarren/spack,mfherbst/spack,iulian787/spack,TheTimmy/spack,mfherbst/spack,skosukhin/spack,tmerrick1/spack,LLNL/spack,tmerrick1/spack,matthiasdiener/spack,mfherbst/spack,skosukhin/spack,mfherbst/spack,EmreAtes/spack,matthiasdiener/spack,skosukhin/spack