UE4 wrapper 4.24 update and Linux build

[gaborpapp]

Built the wrapper in Linux with the latest UE 4.24.

[dorodnic]

Hi @gaborpapp
Thank you for the Pull-Request!
Currently CI is rejecting the patch due to the following:
[ERROR] include/librealsense2/hpp/rs_processing.hpp has tabs (this project is using spaces as delimiters)

[gaborpapp]

Thanks @dorodnic . Sorry, fixed the tab issue.

[dorodnic]

I'm somewhat of UE newbie, do you have some documentation on setting-up UE on Linux?
I want to give it all a try before merging

[gaborpapp]

I'm not very experienced either, but it's not difficult to set up. This can help:
https://docs.unrealengine.com/en-US/Platforms/Linux/BeginnerLinuxDeveloper/SettingUpAnUnrealWorkflow/index.html
I built it with the latest 4.24-preview-3 branch, but I hope it works with the release branch as well.

[dorodnic]

Thanks (Still working on it, in-between other things)

[dorodnic]

It works! 🎉 🎉
After many hours of fiddling around with Linux Vulkan drivers I can confirm everything is working on Ubuntu 16 and Windows with UE 4.24
Again, thank you so much for taking the time to port the wrapper to Linux!
I had two small questions - @gaborpapp

1. Given 4.24 is not officially out yet, does this PR depends on 4.24 or can it work with say 4.23?
2. To fix final linker errors on Linux, I had to do something to the extent of:
   sudo make DESTDIR="/.../UnrealEngine-4.24/Engine/Extras/ThirdPartyNotUE/SDKs/HostLinux/Linux_x64/v15_clang-8.0.1-centos7/x86_64-unknown-linux-gnu" install from librealsense build folder. Is this the correct method for passing dependencies into engine build? (I couldn't find anything on it from google) I'll try to update readme.mp accordingly with my steps, but I'd like to learn what is the proper way of doing this. Any info would be appreciated.

[gaborpapp]

Great!

1. I will try it with 4.23, I rebuild the editor and get back to you.
2. I don't remember any linker errors. UE4 just could not find the librealsense library when the project was loaded, but setting LD_LIBRARY_PATH solved it.

[gaborpapp]

I made changes for UE 4.23 tested with the latest release 4.23.1. Now this should compile with 4.23 and 4.24 as well.

On my Fedora 30 UnrealEditor cannot load the plugin without running export LD_LIBRARY_PATH=/usr/local/lib64 first. This could be solved by statically linking librealsense to the wrapper plugin if necessary.