Replaced CMAKE_SOURCE_DIR, so WickedEngine can be used as submodule

[mlavik1]

Suggested fix for #788

Test case:

1. Create a new CMake-based project
2. Add WickedEngine as a subdirectory
3. Add add_subdirectory(WickedEngine) to your CMakeLists.txt, and also link to WickedEngine (target_link_libraries(MyProject WickedEngine))
4. Build your project.

Of course, feel free to reject if you can think of a better fix, or if you don't feel this is a necessary change. Though, I can imagine there are others out there who also wish to use WickedEngine like this :)

[portaloffreedom]

I like the idea! I need first to test if this breaks the cmake install flow, otherwise it's good to go for me!

[portaloffreedom]

I don't think this needs to be a CACHE entry, as we don't want to expose this variable to the user configuring the project

[mlavik1]

You're right. i originally did that to make it acceasible from parent directories, but realise now that's silly, since the path should be known anyway. I'll fix that today or tomorrow 😃

[mlavik1]

I like the idea! I need first to test if this breaks the cmake install flow, otherwise it's good to go for me!

Ok, cool! I'll test that as well 😃 I suppose that shouldn't be affected, but it definitely needs testing😅

[mlavik1]

Hi @portaloffreedom, I updated my PR. WICKED_ROOT_DIR is no longer a cached variable.
Feel free to let me know if there's anything else.
Have a great week! :)