* guix/build/emacs-build-system.scm (%standard-phases): Reinstate the check
phase from the gnu-build-system.
* guix/build-system/emacs.scm (emacs-build)[tests?]: But do not enable it by default.
[parallel-tests?]: Add argument.
Signed-off-by: Ludovic Courtès <ludo@gnu.org>