Fix idempotence of `utils/build-gnu.sh`
Fix idempotence of `utils/build-gnu.sh`

* Fix regular expressions to only match when run the first time.
* Enhance the regular expression which removes duplicated "/usr/bin/" to
  allow a space between them (+ also consider `init.cfg`).

uutils/coreutils,uutils/coreutils,uutils/coreutils