message: Try to install Eigen on Windows and Ubuntu
  * Install Eigen before building Python wheels
  Should allow more modern CMake usage
diff: @@ -4,7 +4,14 @@ set -ev
  pip install cibuildwheel==2.0.0
  if [[ $RUNNER_OS == "Windows" ]]; then
  - git clone --recursive -b 3.3.9 --depth 1 https://gitlab.com/libeigen/eigen /c/eigen
  + git clone --recursive -b 3.4.0 --depth 1 https://gitlab.com/libeigen/eigen /c/eigen
  + cd /c/eigen
  + mkdir build
  + cd build
  + cmake .. -DCMAKE_INSTALL_PREFIX=/c/eigen-34
  + cmake --build . --target install
  elif [[ $RUNNER_OS == "macOS" ]]; then
  brew install eigen
  +else
  + sudo apt install libeigen3-dev
  fi
  