Handle FindOGRE module's differing definitions

[cottsay]

The FindOGRE CMake module sets separate include directory values for each component, so if OGRE is found using this mechanism, we need to list those directories as well.

For reference, here is where FindOGRE sets the per-component include directories: https://github.com/OGRECave/ogre/blob/7eaa819fb722838b0b981f2bc505726c5ee05348/CMake/Packages/FindOGRE.cmake#L468

[rhaschke]

Which version of OGRE you are compiling against that you observe issues with? I didn't notice any issues so far.
Also, I would expect that libs and includes for all components are accumulated in OGRE_LIBRARIES and OGRE_INCLUDE_DIRS variables. At least that's the behaviour I'm used to for catkin and Boost.

[cottsay]

Which version of OGRE you are compiling against that you observe issues with?

Any OGRE version prior to 1.11 could contain FindOGRE.cmake and manifest this issue. Fedora 33 packages 1.9, which is where I hit this issue.

[rhaschke]

Ubuntu, the reference distro for ROS, also ships OGRE 1.9 - and we didn't observe any issues in the past. Oh, wait: On Ubuntu, the cmake files are installed in a non-standard location and thus are not found automatically. Thus we fallback to pkgconfig!

I fixed this issue in 65ea752 in a way to be compatible with more recent versions of OGRE, where all include dirs and libraries are collected in OGRE_INCLUDE_DIRS and OGRE_LIBRARIES variables resp.