Fix pg_upgrade test on Cygwin

The verification of permissions doesn't succeed on Cygwin, because the
required feature is not implemented for Cygwin at the moment.  So skip
this part of the test, like MinGW already does.

src/bin/pg_upgrade/test.sh

@@ -232,7 +232,7 @@ pg_upgrade $PG_UPGRADE_OPTS -d "${PGDATA}.old" -D "$PGDATA" -b "$oldbindir" -p "
 # make sure all directories and files have group permissions, on Unix hosts
 # Windows hosts don't support Unix-y permissions.
 case $testhost in
-	MINGW*) ;;
+	MINGW*|CYGWIN*) ;;
 	*)	if [ `find "$PGDATA" -type f ! -perm 640 | wc -l` -ne 0 ]; then
 			echo "files in PGDATA with permission != 640";
 			exit 1;
@@ -240,7 +240,7 @@ case $testhost in
 esac
 
 case $testhost in
-	MINGW*) ;;
+	MINGW*|CYGWIN*) ;;
 	*)	if [ `find "$PGDATA" -type d ! -perm 750 | wc -l` -ne 0 ]; then
 			echo "directories in PGDATA with permission != 750";
 			exit 1;