Added check if user specified drive location

This is for --aucdtect.  If the user specified a location
in the Cygwin environment to check for FLAC files, but specified
the drive letter:

  redoflacs -a C:/cygwin/path/to/flacs/directory

We now check for that and remove 'C:/cygwin' which properly
allows the script to search in the Cygwin environment since
it's local to it