Function check_build 

pub fn check_build(
    tree: &Path,
    cwd: Option<&str>,
    cmd: Option<&str>,
    env: &[(String, String)],
    notes: &mut Vec<String>,
) -> Result<(), Fail>

Run the recipe for the compile alone, no artifact check — the shape an extra publish gate wants: its CARGO_TARGET_DIR points somewhere the bin: convention does not, and success IS its whole verdict.