guix build: Factorize common options.

* guix/scripts/build.scm (show-build-options-help,
  set-build-options-from-command-line): New procedures.
  (show-help): Remove description of --dry-run,
  --fallback, --no-substitutes, --max-silent-time, and --cores.  Call
  'show-build-options-help'.
  (%standard-build-options): New variable.
  (%options): Remove --dry-run, --fallback, --no-substitutes,
  --verbosity, --max-silent-time, and --cores.  Add
  %STANDARD-BUILD-OPTIONS.
  (guix-build): Use 'set-build-options-from-command-line' instead of
  'set-build-options'.
* guix/scripts/archive.scm (show-help): Remove description of --dry-run,
  --fallback, --no-substitutes, --max-silent-time, and --cores.  Call
  'show-build-options-help'.
  (%options): Remove --dry-run, --fallback, --no-substitutes,
  --verbosity, --max-silent-time, and --cores.  Add
  %STANDARD-BUILD-OPTIONS.
  (export-from-store): Call 'set-build-options-from-command-line'
  instead of 'set-build-options.