Bump uutils recipe to version with fix for mv bug

See merge request redox-os/cookbook!367

Add a recipe for "Hello World" examples

See merge request !363

Update uutils recipe

See merge request !362

xz: update and change to git

See merge request !361

the xz backdoor caused github to disable the repo. Changing to
the tukaani git to allow builds to happen.

Moved from tarball to git clone for building xz to avoid any
other potential tarball poisoning by JiaT75, using the commit
tagged as 5.2.5; the latest full release tag available without
any commits by JiaT75.