Function implicit_install_script 

pub fn implicit_install_script(
    manifest: &PackageJson,
    has_binding_gyp: bool,
) -> Option<&'static str>

Single source of truth for the implicit node-gyp rebuild fallback: returns Some("node-gyp rebuild") when the package ships a binding.gyp at its root AND the manifest leaves both install and preinstall empty (either one is the author’s explicit opt-out from the default).

has_binding_gyp is passed by the caller so this helper is agnostic to how presence was detected — the install pipeline stats the materialized package dir, while aube ignored-builds reads the store PackageIndex since the package may not be linked into node_modules yet. Both paths must agree on the gate condition, so they both go through this.