def write_script_for(gem_name, filespec = DEFAULT_SCRIPT_NAME)
      File.write(filespec, script_for(gem_name, filespec))
      FileUtils.chmod("u=wrx,go=rx", filespec)
    end
def write_script_for(gem_name, filespec = DEFAULT_SCRIPT_NAME)
      File.write(filespec, script_for(gem_name, filespec))
      FileUtils.chmod("u=wrx,go=rx", filespec)
    end
Writes to file a a shell script that will test the gem (see above for details),
 and sets the permission to be executable so it can be run as a shell command.