LLVM backend

[thi8v]

For the code generation and compilation (LLVM related crates), in the Zom compiler. We could replace it with the C++ library, because it's the official way to use LLVM, there is some issues in this project that is related to LLVM not working : #24, #20, #23, #21. If we replace it with an a C++ package, we could just follow the doc and not wasting its time to found the function in Inkwell, etc ..

Pros

• We can follow the LLVM docs without any trouble to find the corresponding function in Inkwell
• Some issues (Fix the CI #24, Fixing builder #20, Impl llvm #23, CI bug #21) could be solved.

Cons

• Safety, C++ is safer than C but C++ is not safe as Rust is.
• Some layer between Rust and C++ is needed, you can find some solution below,

Solution N°1

Write a serializer that serialize the result of the type checking (or the end of the compilation pipeline that doesn't need LLVM). And the C++ program will be executed in a child process, with the serialized input, and we deserialize and return the output desired by the compiler.

Solution N°2

Write a C++ lib that uses LLVM and emit the desired output by the compiler, and his functions is called by the the Zom compiler with the Rust FFI to C++.

Originally posted by @Larsouille25 in #25 (comment)