From - Generate project solution without Engine project - C++ Programming - Unreal Engine Forums
To save a click here’s a batch file I’ve been using (substitute your paths for anything in {})
"{EPIC_GAMES_PATH}\{UE_VERSION}\Engine\Binaries\DotNET\UnrealBuildTool.exe" -projectfiles -project="%~dp0{PROJECT_FILE_NAME}.uproject" -game
PAUSE
Unfortunately the engine source seems to always be included now, so while this didn’t solve the question I linked (and found it from) it does nicely solve this problem… except now I’d really love to have a .sln without the UE4 source as it does slow down intellisense and VAX quite a bit 
Also psssst, Epic… document your cmd line APIs kthx 