Function resolve 

pub fn resolve(
    tb: &dyn Toolbox,
    override_path: Option<&Path>,
    bynk_bin_dir: Option<&Path>,
    driver: Version,
) -> Compiler

Resolve bynkc against a Toolbox, given the override (typically std::env::var("BYNK_BYNKC")), the directory of the running bynk binary (for the sibling fallback), and the driver’s own version (to classify skew).