[FEATURE REQUEST] BCL needs a cross-platform runtime

[ArachnidAbby]

Description of the feature

The language needs some kind of cross-platform runtime instead of relying on the gcc C runtime. (I believe we use crt1 found in /lib on linux?). This will eventually bring us closer to full windows and mac support.

Benefits

This not only allows a larger degree of control over the execution of code in BCL, but we can also have things like default initialized global variables which are otherwise impossible without a runtime to ensure that those global actually get initialized.'

Features needed to accomplish this

• [x] Compiler directives for platform
• [ ] multi-platform support for the standard library, meaning we need to stop binding libc functions
• [ ] consts, this isn't completely required, but makes it much easier
• [ ] compiler emitting necessary constants available at RT compilation time (CRT gets recompiled and linked in, not imported)
• [ ] compiler flag that can be set to use a custom runtime
• [x] typedef for windows type definitions

Changing the runtime at compilation

bcl compile main.bcl --emit-binary --run --rt=myCustomRuntime.bcl

Possible issues that may make this feature difficult to implement

Creating a runtime can run into many issues, especially a cross-platform one. Not to mention trying to ensure everything works while updating BCL may be a pain. It may be worth looking into setting up something like azure devops. Unfortunately this is hard to setup as compiling llvmlite (a necessary dependency) is annoying. Especially as of recently.

[ArachnidAbby]

turns out this is less possible than I thought. We must rely on the c runtime, but we can use the libc entry symbol. This basically means we use 2 runtimes. very fun.