Hello,
I had no problem build all the previous version UE4 ( up to 4.2.1 ) using Visual Studio 2012 …
In the past two days, I had downloaded UE4.3 version, and I never able to build the engine with Visual Studio 2012 anymore…
The build actually crashed “Microsoft C/C++ Compiler Driver” and I believe it happened when it comes to
23> PCH.UnrealEd.UnrealEd.h.cpp
23> PCH.Engine.EnginePrivate.h.cpp
Since the crashed of the Compiler Driver, it means the whole build will never completed with the error:
UBT error : Failed to produce item: UE4Editor-UnrealEd.lib
I had tried it with two different machines (Visual Studio 2012) and the same crash happened…
Any advise would be much appreciated…
PS: Just for information, I have no issue of building UE4.3 on Visual Studio 2013 … but I do need the UE4.3 to be build with Visual Studio 2012 because our academic institute does not want to support VS2013… 
Thanks
K