Write tests for NSZ

[alucryd]

Same as RVZ, I need to produce a valid legal dummy NSP file to write tests for NSZ.

[leo60228]

The .nsp extension is used for both any PFS0 (i.e. exefs.nsp) as well as specifically a PFS0 containing NCAs. If the former is all that's needed for testing, you can easily make one from a directory with linkle pfs0 (among other tools, though linkle is probably the easiest to install if you already have Cargo).

[leo60228]

Tooling for creating NSP files containing applications is limited, as it is generally unnecessary for homebrew and they cannot be used on-console without piracy tools.