[Clfs-dev] XZ Utils in chapter 6

[Ken Moffat]

Why ?

I can see that in (at least) x86_64 and x86_64-64 this is included in a
page-by-page path through chapter 6.  In ppc64, it isn't.  So, I built
a chroot ppc64 without it last month.  Works fine.

The obvious fix would be to correct the links in ppc64 to match the
other books, but is there really a reason why we need this before we
build the final system ?  Yes, I understand the "compresses better"
idea (even though my own tests haven't identified any use case where
the difference is significant), but unless it is available on the host it
can't be used for any packages which appear before chapter 9.

Please note that I haven't moved to git yet, so I won't be altering
this.  Feel free to fix it if there is consensus.

ĸen