fix(build): add missing eigen dependency

[quantum9Innovation]

close #543

[wentasah]

Suggested change

	<depend>eigen</depend>
	<depend>eigen</depend>
	<build_depend>pkg-config</build_depend>

I think that <build_depend>pkg-config</build_depend> should be added too. Without it, I'm getting this error:

...
> -- Found tf2_ros: 0.25.6 (/nix/store/6pxj2y6qkl5wlfmhjypkb9j4j95pmij9-ros-humble-tf2-ros-0.25.6-r1/share/tf2_ros/cmake)
> -- Found velodyne_msgs: 2.4.0 (/nix/store/xm5qphp0mqs8dbq14328g25ph8fys0im-ros-rolling-velodyne-msgs-2.4.0/share/velodyne_msgs/cmake)
> CMake Error at /nix/store/jacf2kn4dfj99c3ywbvfyg6w53xvxsfl-cmake-3.27.8/share/cmake-3.27/Modules/FindPackageHandleStandardArgs.cmake:230 (message):
>   Could NOT find PkgConfig (missing: PKG_CONFIG_EXECUTABLE)
> Call Stack (most recent call first):
>   /nix/store/jacf2kn4dfj99c3ywbvfyg6w53xvxsfl-cmake-3.27.8/share/cmake-3.27/Modules/FindPackageHandleStandardArgs.cmake:600 (_FPHSA_FAILURE_MESSAGE)
>   /nix/store/jacf2kn4dfj99c3ywbvfyg6w53xvxsfl-cmake-3.27.8/share/cmake-3.27/Modules/FindPkgConfig.cmake:99 (find_package_handle_standard_args)
>   CMakeLists.txt:29 (find_package)

[clalancette]

Yes, you are correct that we also need pkg-config here.

That said, this should be temporary, as nowadays we should be able to find yaml-cpp with pure CMake. But that will be a separate PR.

[clalancette]

Given that I wasn't able to push here, I ended up opening a new PR in #545 to add in the pkg-config dependency. Thanks for this, I'm going to close this out and merge that one instead.