Prefer PROJECT_SOURCE_DIR over CMAKE_SOURCE_DIR

[Aaron-SP]

When bundling JSBSIM as an external project using CMAKE FetchContent, JSBSIM is not configured because it uses CMAKE_SOURCE_DIR instead of PROJECT_SOURCE_DIR.

CMAKE Issue Explained

I've made a fork with this change at repo.

Does it make sense to make this change to expand packaging capabilities of JSBSim with CMAKE?

[bcoconni]

Thanks for reporting this issue.
Would you mind submitting a pull request from your repo ?

[Aaron-SP]

I have opened a pull request here. This fixes my issue but I did not check building the extra modules such as Python etc. We might want to double check that any files that code generate CMAKE are also updated, not sure.

[bcoconni]

Your pull request has been merged.
Thanks for your contribution 👍