If you make any changes to the ThirdParty libs in here, or need to compile them for a new VS version or platform, then you can use the batch/command files included as a starting point.

Go to [UE4_Install_Dir]\Engine\Build\BatchFiles and execute:

RunUAT BuildThirdPartyLibs -SearchDir=Engine/Plugins/Experimental/Paper2D/Source/ThirdParty

This will set up the environment for compiling, find the appropriate build script for each library (e.g., Box2D/UE4_BuildThirdPartyLib.bat) and execute it, building up a new changelist in P4 with the modified library files.

[Replace SearchDir with a hard path to this directory if it's not rooted in the same place as the engine]