* gnu/installer/utils.scm (run-shell-command): Add #:locale and honor it.
* gnu/installer/newt/final.scm (run-install-shell): Add 'locale'
parameter; pass it to 'install-system'.
(run-final-page): Obtain locale from RESULT; pass it to 'run-install-shell'.
* gnu/installer/final.scm (install-system): Add 'locale' parameter; pass
it to 'run-shell-command'.