JPM won't start on arch linux (installed from package `janet-lang-git` 

Here's the error message:
```
$ jpm
exec: Failed to execute process '/usr/local/bin/jpm': The file specified the interpreter '/usr/local/bin/janet', which is not an executable command.
$ JANET_PATH=(which janet) jpm # I am using fish
exec: Failed to execute process '/usr/local/bin/jpm': The file specified the interpreter '/usr/local/bin/janet', which is not an executable command.
```