Support building on Windows and Linux with the same script

[copyrite]

To facilitate collaboration between users on different platforms, build_common.ps1 should seek to integrate the Linux workflow.

That is, it should become possible to do the following:

1. Alice starts a new mod project using X2MBC and version controls it (X2MBC included)
2. Bob, on another platform, clones Alice's mod project and is able to build without modifying the X2MBC in the repo.

For changes made in-place into the script, see X2 Linux VSCode Project Template on r/xcom2mods, or the same changes on my fork.

Probably requires some instructions in README.md to be updated as well, since .vscode/tasks.json is often version controlled as well.