Debian adds LoongArch support

The Debian project has added
the LoongArch architecture to its ports collection.

After an initial manual bootstrap of roughly 200 packages, two
buildds are now building packages for the newly added 'loong64'
port with the help of qemu-user. After enough packages have been
built for the port to be self-hosting, we're planning to replace
these two buildds with real hardware hosted at Loongson.