I have no clue which talk you are refering to, but relying on a virtual machine that is not available everywhere is not making your stuff system independant.
If you really want your scripts to be system independant, than there is nothing you can do. Your scripts will always ever target either windows or linux or mac, you can combine linux and mac in a sense, but thats it.
Best efford system independance is done by using only things that are available in busybox and also using only simplest features of sh, not the fancy extensions given by bash, dash or zsh or others.
But to be honest, your scripts will always depend on the things you want to automate…
