Using the preprocessor before generating prototypes provides some
"niceties" but the places that rely on these are pretty few.
Vastly simplifying the BUILD SYSTEM is a better trade-off.
Unbalancing { } blocks due to the preprocessor is cringe anyway (think
of the tree-sitter trees!), write these in a different way.
Add some workarounds for plattform specific features.
INCLUDE_GENERATED_DECLARATIONS flag is now technically redundant,
but will be cleaned up in a follow-up PR as it is a big mess.
79c8159f41