FLANN build failure in CMAKE 3.16.3 and GCC 9.3.0

[slamajakub]

Build of FLANN 1.9.1 fails on Ubuntu 20.04, using cmake 3.16.3 and gcc 9.3.0. Build fails due to a cmake error

CMake Error at src/cpp/CMakeLists.txt:86 (add_library):
No SOURCES given to target: flann
CMake Error at src/cpp/CMakeLists.txt:32 (add_library):
No SOURCES given to target: flann_cpp

The issue is inside FLANN library, as reported in FLANN/#443.

A possible fix is to add an empty file and specify it as a source (instead of empty list) on the reported lines in CMakeLists.txt file. Such a solution is also reported as a workaround in the aforementioned issue. Since installation of FLANN is done from sources, this fix could be incorporated in the build pipeline of this wrapper.