more gnu compatible

// ======================== Makefile methods ========================

const Rule* Makefile::find_explicit_rule(const std::string& target) const {

    // A target may have several explicit rules: GNU make merges their

    // prerequisites but only one rule carries the recipe. Prefer the

    // recipe-bearing rule so the target is actually built; fall back to the

    // last prerequisite-only rule otherwise. Kbuild relies on this: the

    // host-program link rule ("conf: FORCE" with a recipe) is separate from

    // the multi_depend-generated "conf: conf.o ..." prerequisite rule.

    const Rule* fallback = nullptr;

    for (auto it = rules.rbegin(); it != rules.rend(); ++it) {

        if (it->is_pattern) continue;

        for (const auto& t : it->targets) {

            if (t == target) return &(*it);

            if (t == target) {

                if (!it->recipes.empty()) return &(*it);

                if (!fallback) fallback = &(*it);

                break;

            }

        }

    return nullptr;

    }

    return fallback;

}

const Rule* Makefile::find_pattern_rule(const std::string& target, std::string& stem) const {