Fix wsssh-server Debian package build - missing /usr/sbin directory

- Added mkdir command to create /usr/sbin directory in wsssh-server debian/rules
- Fixed 'No such file or directory' error when installing wssshd-watchdog
- Ensures proper directory structure for watchdog script installation
- Resolves build failure when running build.sh --packages or --debian-only
- Maintains consistency with other directory creation commands

wsssh-server/debian/rules

@@ -111,6 +111,7 @@ override_dh_auto_install:
 	mkdir -p debian/wsssh-server/var/lib/wssshd
 	mkdir -p debian/wsssh-server/var/log/wssshd
 	mkdir -p debian/wsssh-server/etc/wssshd
+	mkdir -p debian/wsssh-server/usr/sbin
 
 	# Install PyInstaller binary
 	install -m 755 dist/wssshd debian/wsssh-server/usr/bin/