Allow to opt-out from shebang mangling for specific paths/shebangs
    
    Introduces __brp_mangle_shebangs_exclude_from and __brp_mangle_shebangs_exclude
    
     * the first allows to explude specific paths from the mangling
     * the second allows to exlude specific shebangs
    
    Both are used with `grep -E`. Similar escaping rules as in [1] apply.
    
    [1] https://fedoraproject.org/wiki/Packaging:AutoProvidesAndRequiresFiltering