openmpi-2.1.1-9.fc28.x86_64 doesn't use the full LDFLAGS from redhat-rpm-config, due to the usual libtool problem. I will try to rebuild it with the current flags, which changed since February and are supposedly more friendly to libtool.
openmpi-2.1.1-10.fc28 has been submitted as an update to Fedora 28. https://bodhi.fedoraproject.org/updates/FEDORA-2018-6243955a16
The rawhide build should be okay.
openmpi-2.1.1-10.fc28 has been pushed to the Fedora 28 testing repository. If problems still persist, please make note of it in this bug report. See https://fedoraproject.org/wiki/QA:Updates_Testing for instructions on how to install test updates. You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2018-6243955a16
openmpi-2.1.1-10.fc28 has been pushed to the Fedora 28 stable repository. If problems still persist, please make note of it in this bug report.