A problem was reported on the mailing list that results in the build failing while linking `NekMesh` on Ubuntu 18.04 (and presumably also recent Debian distros?). The error that is received is: ``` //usr/lib/x86_64-linux-gnu/libpng16.so.16: undefined reference to `inflateValidate@ZLIB_1.2.9' collect2: error: ld returned 1 exit status utilities/NekMesh/CMakeFiles/NekMesh.dir/build.make:1021: recipe for target 'utilities/NekMesh/NekMesh' failed make[2]: *** [utilities/NekMesh/NekMesh] Error 1 ... ``` This occurs when `NEKTAR_USE_MESHGEN=ON` and `THIRDPARTY_BUILD_ZLIB=ON` when using the packaged version of OCE in Ubuntu (OCE 0.17). It looks like this is a result of an incompatibility between `zlib-1.2.7`, the version used by Nektar++ in a third party build, and `libpng16.so.16` provided with Ubuntu 18.04. (See this [bug report](https://bugs.launchpad.net/ubuntu/+source/libpng1.6/+bug/1780233) for more info) I verified this by manually running the link command for `NekMesh`, as found in `build/utilities/NekMesh/CMakeFiles/NekMesh.dir/link.txt` and getting the error. If the reference to `../../ThirdParty/dist/lib/libz.a` is removed from the link command and the libz library files are removed from the ThirdParty/dist/lib directory, the linking picks up the system libz and completes successfully.