Version 1.6.1 is available upstream. Please consider updating! It seems that version 1.6.1 is available upstream, while the latest version in the Gentoo tree is 9999. You think this warning is false? Read more about it here.
nanoflann is a C++ header-only library for building KD-Trees,
mostly optimized for 2D or 3D point clouds. This library is a fork
(and a subset) of the library.