This is a followup togn-latest-20200428
7e6d8d366a. It means that "make check-system" can run tests from (gnu tests install) much faster because it does not need to build a full 'guix' package. * gnu/ci.scm (channel-instance->package): Export. * build-aux/run-system-tests.scm (tests-for-channel-instance): New procedure, with code formerly in 'run-system-tests'. (run-system-tests): Call 'interned-file' for SOURCE, and add call to 'tests-for-channel-instance'.