Add libigl

[SimonDanisch]

[eschnett]

The error message CMake Error: The source directory "/workspace/srcdir/libigl/build/ " is weird. Note the trailing space.

You can try building in the main directory. For that, remove the mkdir build and cd build commands, and add the option -B build to cmake. Then build and install via

cmake --build build --parallel $(nproc)
cmake --install build

[fingolfin]

What's the status of this? @SimonDanisch are you still interested in getting this in (after waiting for over a year.. oops...) It seems it was not building last someone commented, but we'd have to do a fresh build now either way, so you could e.g. rebase it onto lastest master or so to get current build logs.