this is important because this 4.0 "Bootstrap" is the one generally used on host "build".


Build-tools/Bootstrap:
  If the source tree does not contain any "Docs/Images/Makefile*" (due to an error,
  or because it is not yet prepared to contain the Images in the source tar-ball),
  a plain "rm" will fail and so cause "Bootstrap" to fail. (This has happened ...)
  Prevent this danger by using "rm -f".