[llvm-ranlib] Update expected error message check for Windows

On Windows hosts, the error message will be something like
`c:\src\llvm-project\out\gn\bin\llvm-ranlib.exe: error: Invalid option: '--D'`.
Due to the .exe after llvm-ranlib the existing CHECK lines do not match.
Fix this by ignoring the program name and starting the check line at "error:".