clang's level for every hook of the project. wasm-opt always shrinks the result after it.
Where #include "…" looks after the including file's folder and the project's top, like clang's -I, separated by commas. Their headers take the place of the standard ones of the same name. A folder the project does not have is skipped.
Kept in .xwcode/settings.json in the project, so a download of the project carries it.