Add support of version

[0xE1E10]

A few changes while we're there:

• Use check_packages() function for prerequisites. So if a new version of wget is released, we don't try to update it and create churn on all Docker layers below us.
• Use force option in ln in case LLVM is already installed in base container but at the wrong version.
• Add ld.lld link.

[0xE1E10]

Latest commit installs all LLVM packages. Reasoning is that if someone is using this feature instead of the default C++ package, he probably need something special from LLVM. Until someone add options to select specific features (14 of them as of today), it's probably easier to just install all of them.

[jcbhmr]

Cool! You seem to know what you're doing; I've added you as a collaborator to this repo. You can merge your own PR! 🥳🎉 Feel free to make any other changes you want to -- I'm not an LLVM expert.

[0xE1E10]

Looks like it fails on Ubuntu Jammy in the test. I've been testing it on the universal image from MS based on Focal. I'll debug that before merging.