Turns out that Nushell doesn't like `-lic` and `&&`, but works perfectly
fine with `-l -i -c` and `;`, which the other shells do too.

These all work:

    bash -l -i -c 'echo lol; /usr/bin/env -0'
    nu -l -i -c 'echo lol; /usr/bin/env -0'
    zsh -l -i -c 'echo lol; /usr/bin/env -0'
    fish -l -i -c 'echo lol; /usr/bin/env -0'

Release Notes:

- Fixed shell environment not being loaded if Nushell was set as
`$SHELL`.