configure.exe: Fix line feed character

config.summary has been opened in text mode, so the line feed character
should be "\n" instead of "\r\n".

Change-Id: Id73b0d698487cdd6f48902f3ae988c6a9fa59407
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>