prefer system-installed contrib libraries
Gmsh distributes numerous third-party packages in
contrib/. While I'm not a big can of this, I understand the motivation of making it easier for the end-user. (A cleaner option would be to provide an install script that downloads and installs all dependencies, and gmsh. This takes unnecessary complexity outside of the source tree.)
Some of the packages might already be available on the system; pretty common are voro++ and tetgen, for example. It'd be great if gmsh could prefer those system-installed packages and fall back to
contrib/ if they aren't found.