After upgrading my project from 4.13 to 4.14 I did a full rebuild on the code and got the following error in my output window:
2>C:\Program Files (x86)\MSBuild\14.0\bin\Microsoft.Common.CurrentVersion.targets(1611,5): warning : The referenced project '..\DotNETCommon\DotNETUtilities\DotNETUtilities.csproj' does not exist. [C:\Program Files (x86)\Epic Games\4.14\Engine\Source\Programs\UnrealBuildTool\UnrealBuildTool.csproj]
2>CSC : error CS2001: Source file 'C:\Program Files (x86)\Epic Games\4.14\Engine\Source\Programs\UnrealBuildTool\..\DotNETCommon\MetaData.cs' could not be found. [C:\Program Files (x86)\Epic Games\4.14\Engine\Source\Programs\UnrealBuildTool\UnrealBuildTool.csproj]
2>EXEC : Clean error : Failed to build UnrealBuildTool.
I can just hit build to actually get the project to compile so it’s a pretty simple work around. I also tested on a brand new, blank C++ project and receive the same error.