Yes, I think so.
For the archives a little bit of background:
flann bundles liblz. Flann not only exposes lz4 in its header but also
flann-using packages directly call lz4-functions when using flann
functions. Debian has patched flann to use the system liblz (both
because bundled libraries suck when there is a security update and
because it caused breakage.). Now a package using flann needs to also
link against the system liblz.
When using pkgconfig this just works. Which is what the patch does.
cu Andreas