checkpkg: use sdiff -s to show differences in the file lists

This makes it much better readable especially for very large file lists.

checkpkg

@@ -82,7 +82,7 @@ for _pkgname in ${pkgname[@]}; do
 	sort -o filelist-$_pkgname filelist-$_pkgname
 	sort -o filelist-$_pkgname-old filelist-$_pkgname-old
 
-	diff -u filelist-$_pkgname-old filelist-$_pkgname
+	sdiff -s filelist-$_pkgname-old filelist-$_pkgname
 
 	if diff filelist-$_pkgname-old filelist-$_pkgname | grep '\.so' > /dev/null 2>&1; then
 		mkdir -p pkg