Found the Linux with fftw3 installed twice:
* in normal way via the package manager in /usr/lib, shared version of the library.
* In /usr/local/fftw3.a, i.e. static version of fftw3 library, probably as some prehistorical remnants.
Our 'cmake' machinery finds static version, and then 'make' fails because of the missed -fPIC compiler key.
We had in the past similar case with static Python installed in the system. Our cmake was able to distinguish it, and then was adding -fPIC keys automatically (thanks to BornAgainMacros file which is gone by now).] now).
* Easiest minimal action would be to force 'cmake' to fail, if static fftw3 found.
** May be introduce description in Troubleshooting, explaining the case. Very likely -DCMAKE_PREFIX_PATH=/usr would fix the problem.
* we can repeat a trick with fftw3.a determination and adding -fPIC key
** But then, very likely, it would lead to mixing fftw3 library and headers from different installations.