[omplapp] Use external dependency ompl via CMake target instead of embedding

[WangWeiLin-MV]

Hi,

I am a member of the VCPKG project. I found that omplapp repeatedly builds "ompl" from the submodule instead of depends on the built libraries https://github.com/microsoft/vcpkg/pull/40151.

I see that ompl/ompl#1066 ompl/ompl#1067 adds the CMake targets ompl::ompl, which allow for convenient target_link_libraries(main PRIVATE ompl::ompl), but omplapp not uses it, and it bypasses ompl/CMakeLists.txt to compile its components like this omplapp/CMakeLists.txt#L252-L257:

add_subdirectory(ompl/doc)
add_subdirectory(ompl/src)
add_subdirectory(ompl/py-bindings)
add_subdirectory(ompl/tests)
add_subdirectory(ompl/demos)
add_subdirectory(ompl/scripts)

And there are many different parts between the two files omplapp/CMakeLists.txt and ompl/CMakeLists.txt. Splitting the two projects need a lot of changes.

I would like to ask if it is possible to modify omplapp to be a project that depends on ompl, rather than an ompl variant that shares a lot of code? This is very helpful to us, and I think this will also make it easier to develop omplapp.

If you have any questions please let me know. Thanks in advance.

[Ryanf55]

Yes, agree. It will be easier after this PR. https://github.com/ompl/omplapp/pull/13

If omplapp called find_package(ompl CONFIG) before it brought it in as a submodule, would that fix it for you?

[WangWeiLin-MV]

If omplapp called find_package(ompl CONFIG) before it brought it in as a submodule, would that fix it for you?

Yes, the duplicate build could be avoided in that way.

[Ryanf55]

@mamoll Can you move this to omplapp? This issue is specific to omplapp

[zkingston]

@Ryanf55 done.