Add GPLv2 alternative for fatlabel

The dosfstools were downgraded to v2.11 after switching to the nogplv3 image. This version of dosfstools has no partition labeling tool.

Mtools is a collection of utilities to access MS-DOS disks from GNU and Unix without mounting them. One of the tools is mlabel, which is a tool for changing the label of FAT partitions.

This is a fix for 746-001602.