Allow non-const statics?

[scottmcm]

@axos88

I also propose the ability to create static variables that are initialized when starting up the application.

This is "life before main", which Rust has been trying to avoid. See previous conversations like

Pre-RFC: Add language support for global constructor functions

Hi! I’ve written up a WIP RFC for adding global constructors, otherwise known as ctors or static initializers. Crates like typetag currently use these constructors, but only support our tier-1 platforms because they depend on rust-ctor. By adding compiler support, we could expand this to all platforms. If anyone could give feedback, either to the wording or the ideas, it would be greatly appreciated! I’ve tried to fill in as much detail as I can, but it’s fairly unrefined. I plan on refining …

The latest direction I remember here is people trying to find a way to meet the main needs without getting problems, such as getting a list of all ______s from multiple crates.