stop "setopt nullglob" from leaking into user's shell

[alinsavix]

In the install_requirements function, we do a setopt nullglob and never attempt to set it back to how it was set previously, which means that the behavior of the user's shell as a whole can (and likely will, as this isn't the default) change globbing behavior without the user's knowledge or consent.

Adding a setopt localoptions before changing any options will cause changed options to reset to their original values when the enclosing function exits, stopping this option change from leaking into the user's shell. See LOCAL_OPTIONS at https://zsh.sourceforge.io/Doc/Release/Options.html for more details