configure: try to fix the disappearing "r" bug in fate

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

configure

@@ -443,7 +443,7 @@ sh_quote(){
 }
 
 cleanws(){
-    echo "$@" | sed 's/^ *//;s/  */ /g;s/ *$//;s/\r//g'
+    echo "$@" | sed 's/^ *//;s/  */ /g;s/ *$//;s/\\r//g'
 }
 
 filter(){