build-infra: Configure fails to find SetEnv.Cmd in microsoft sdk

When configure looks for the SetEnv.Cmd script in a microsoft SDK, it sometimes fails to find it due to not seeing the the cmd file as executable. There is a workaround implemented for this already, but it only works for files ending with .bat or .cmd and not the mixed case .Cmd. To fix this, the greps used to detect the workaround should add -i to make them case insensitive.

This issue has been reported twice from different sources, one internal and one external.