CMake package exports: remove stale absolute OSG paths from imported osgEarth targets

[Copilot]

Downstream builds can fail because installed osgearth-targets.cmake may contain machine-specific absolute OpenSceneGraph library paths (from legacy FindOpenSceneGraph resolution). When consumed on another system, those paths are invalid and break linking.

• Package config import sanitization

  • Added a post-import cleanup step in cmake/osgearth-config.cmake.in to remove absolute path entries in INTERFACE_LINK_LIBRARIES when they point to known OSG/OpenThreads libs (osg, osgDB, osgGA, osgUtil, osgViewer, osgText, osgSim, osgShadow, osgManipulator, OpenThreads).
  • Handles both plain entries and $<LINK_ONLY:...> entries.
  • Preserves non-OSG entries and link keywords (optimized, debug, general).

• Rebind OSG dependencies at consume time

  • After find_dependency(OpenSceneGraph ...), the config now links osgEarth::osgEarth against ${OPENSCENEGRAPH_LIBRARIES} so consumers use their local OSG resolution instead of stale exported absolute paths.

find_dependency(OpenSceneGraph REQUIRED COMPONENTS osg osgDB osgGA osgUtil osgViewer OpenThreads)

# after importing osgEarth::* targets
_osgearth_remove_legacy_osg_paths(osgEarth::osgEarth)

target_link_libraries(osgEarth::osgEarth INTERFACE ${OPENSCENEGRAPH_LIBRARIES})

• Fixes cmake configuration build error #2987