Either use direnv or nix develop .
to enter the shell, devkitarm (the 3DS toolchain)
will get automatically installed, and added to PATH
To build you can use the Makefile
that was provided in the libctru's official examples
or the simple ./build.sh
script, 3dslink
for quick testing should already be in your
PATH
as well, to build and link, you can use the ./build-and-link.sh <IP ADDRESS>
script