Merge pull request #2289 from talregev/TalR/vcpkg_eigen3

Add back eigen3 to vcpkg

Author: dellaert

.github/workflows/vcpkg.yml

@@ -108,6 +108,7 @@ jobs:
           boost-system
           boost-thread
           boost-timer
+          eigen3
           tbb
           pybind11
           geographiclib
@@ -172,7 +173,7 @@ jobs:
               -DGTSAM_BUILD_TESTS=ON \
               -DGTSAM_BUILD_UNSTABLE=ON \
               -DGTSAM_ALLOW_DEPRECATED_SINCE_V43=OFF \
-              -DGTSAM_USE_SYSTEM_EIGEN=OFF \
+              -DGTSAM_USE_SYSTEM_EIGEN=ON \
               -DGTSAM_USE_SYSTEM_METIS=OFF \
               -DGTSAM_USE_SYSTEM_PYBIND=ON \
               -DGTSAM_ENABLE_GEOGRAPHICLIB=ON \