Found a typo
Detect whether Python2 exists when building NaCl game modules and set PNACLPYTHON before executing NaCl build cmds
Ignore NaCl binaries.
Build-depend on NaCl build env. package and use when available.

This package is, essentially, one of the cut-down NaCl SDK tarballs (either
i386 or amd64) prepared by Amanieu d'Antras.
Depend on unv-nacl-runtime; symlink to the required binaries.