Hello it is strange, If I compare the github ufo-filters repository (where sources are comming from) it contains the deps/oclfft directory[1] with all the offending files. Now If I look at the sources in the debian repository[2], there is only the .pc.in file from this directroy.
So something went wrong during the repack process... I need to investigate. Cheers Frederic. [1] https://github.com/ufo-kit/ufo-filters/tree/master/deps/oclfft [2] https://sources.debian.org/src/ufo-filters/0.14.1+dfsg1-1/deps/