Fix Ceres inclusion and path export

[jprestwo]

Ceres is referenced in fuse header files and the existing way it was being included in fuse_core did not export the include paths for Ceres which breaks downstream packages when they include fuse_core headers.

This was only exposed through the per-package builds since the existing merged builds get lucky that all the include dirs are merged together.

[svwilliams]

I want to be really careful here. fuse is a public, open-source repo. I don't want to break anything for official builds of ROS1, end of life though it may be. Do these changes work with older versions of Ceres (2.0, 2.1, etc) and Ubuntu? Should I make a devel branch specific to Ubuntu Jammy and/or Noble?

[jprestwo]

I want to be really careful here. fuse is a public, open-source repo. I don't want to break anything for official builds of ROS1, end of life though it may be. Do these changes work with older versions of Ceres (2.0, 2.1, etc) and Ubuntu? Should I make a devel branch specific to Ubuntu Jammy and/or Noble?

@svwilliams I'm unsure about older versions. But at the high level I think fuse was flat out broken anyways regarding this. I guess everyone out there does --merge-install?

The core issue is that ceres itself doesn't export the proper variables, or at least not INCLUDE_DIRS.

Also, is this fork public? I don't see that it is...
Edit: I'm not well informed ^^^. Its indeed public 🤣

[jprestwo]

Also this bit specifically really is the correct way to do things:

 PUBLIC
    Ceres::ceres
    ${catkin_LIBRARIES}

There are headers in fuse_core which reference ceres headers, so these need to be defined as public otherwise anything including the fuse_core header won't be able to find the ceres headers. I think the big question (even for me) is about pulling in the include directories in somewhat of a non-standard fashion (i.e. not simply using ceres_INCLUDE_DIRS)