I got this error today while developing a powershell script for cloning a GIT repository. The error was "cannot handle CLONE.exe as a builtin". It was a simple clone "GIT CLONE <Source>". I also got it when trying to make a GIT PULL. Turns out that the above command has to be in lowercase. If not it will fail and show the above error. It should have been:
"git clone <Source>"