Still stuck? I was going to wait for it to show up in the repos, but it hasn’t so far. So here’s how I did it (for my regular user account, not system-wide):
git clone https://github.com/NetHack/NetHack
cd NetHack
sys/unix/setup.sh sys/unix/hints/linux.500
Now you’ve got a Makefile in the top-level NetHack as well as the src subdirectory. Find the else #!WANT_SOURCE_INSTALL block in both and edit HACKDIR to set the directory for the game itself and SHELLDIR to set the directory for the launcher script.
(And if I actually knew how to use make, I’d probably have a less clunky method than this. Anyone?)
make fetch-Lua
make all
make install