Generating XCode project from .uproject fails

Using the option Services->Generate XCode Project fails to update the XCode solutuion. This prevents source files added to the project from the directory to show up in the editor.

Regression:
No - the same error appears for a 4.11.2 project following the repro steps provided.

1. Create new C++ Project
2. Open project directory
3. Right click on .uproject
4. Select Services->Generate XCode Project

Result:
Process fails with error shown in Callstack field

Expected:
Process completes and updates the XCode file

MSBUILD: error MSBUILD0000: Project file '../../../Source/Programs/UnrealBuildTool/UnrealBuildTool.csproj' not found. Discovering modules, targets and source code for project...