Fixes RHBZ#1544361
    
    In Rawhide (to be Fedora 28) our current ELF header is not sufficient
    and possible executable bit for a file is dropped:
    
        *** WARNING: ./usr/lib/fun.so is executable but has empty or no shebang, removing executable bit
    
    Extended the make_elf() to add one more byte into the header and added
    some tests, most importantly to check if file permission stays in place.