Allow passing some `ARGV0` (or another environment variable) to executables

[Azathothas]

Hi, I am from pkgforge, we use sharun+wrappe to package hundreds of portable packages at Soarpkgs

Wrappe works wonders for regular packages, but sometimes some packages contain multiple executables.
Sharun itself supports multicalls (like busybox) but when sharun is called from a wrappe packed (or rather unpacked executable), it has no way of knowing what the user passed to wrappe (how wrappe was called).
So this breaks packages that contain multiple executables and doesn't allow for features like single mulitcall busybox like binaries.
See how appimage resolve this: https://docs.appimage.org/packaging-guide/environment-variables.html

I am pretty sure I didn't do a good job explaining, so I will mention @VHSgunzo to do the explaining.
And I think he would also be willing to submit a PR if you are interested in adding such a feature.

Thanks again for this wonderful tool.