Change how binary/lib/dll directories are set

[ptheywood]

Changes CMake archive/binary output directores are set, to be handeleed by updated logic in common.cmake rather than manually in the repository.

Also adds -DFLAMEGPU_ROOT=/path/to/local/FLAMEGPU2 as a mechanism to avoid fetching remote FLAME GPU easily. This will need changing further once we have installation rules.

This change (coupled with the main repo change) does currently lead to libflamegpu.a being placed in build/lib/<config> rather than _deps/flamegpu-builds/lib/<config> which could be reverted to with a change in either repo.

• Re-test and merge after the main repo: Change how the bin/lib paths are set throughout CMakeLists FLAMEGPU2#653
• Once confirmed apply this to other standalone repos.

[Robadob]

Worth moving these changes into the alifetutorial too, I updated that to copy from this yesterday.

[Robadob]

You never did merge my PR. so just modify it I guess.

FLAMEGPU/FLAMEGPU2-tutorial-cudacpp#3

[ptheywood]

You never did merge my PR. so just modify it I guess.

FLAMEGPU/ALifeTutorial#3

I've not got round to testing it yet, but yep the plan was to move it to all the standalone cuda C++ repos once it's narrowed down, which will include the tutorial (especially once we rename it so I don't forget about it in the future)