Your package fails to build with the newest upcoming autoconf-2.71, which is part of a wide Fedora change. Please see the attached copr: https://copr.fedorainfracloud.org/coprs/odubaj/autoconf-2.70/packages/. More information about testing your package when building with autoconf available here: https://fedoraproject.org/wiki/Changes/Autoconf_271#How_To_Test
Gentle ping.
Greetings and thanks very much for reporting. I'm sorry I'm sometimes a bit laggy in responding to issues. I just followed the steps to build stuff locally using mock as described on the wiki page above to reproduce and fix the issues. Other than I expected the build worked fine without any issues and I have some RPMs in my /var/lib/mock/odubaj-autoconf-2.70_fedora-rawhide-x86_64/result. I uploaded the stuff here for review: https://dmaphy.fedorapeople.org/ncmpcpp/. Unfortunately the Copr build seems to be too old and no results are available anymore there. Are you able to trigger a rebuild there to see if the build still fails? Probably with a bit of luck it builds there as well now, we'll see.
Build succeeded, thanks for your effort! Closing this issue.