Update btrfs-progs once again and add static output

[Tobias Geerinckx-Rice]

Hullo Guix,

Some simple patches to add a ‘static’ output to the btrfs-progs
package, containing statically linked versions of all the tools.

It's an eventual requirement for btrfs multi-device root support (the
initrd needs to ‘btrfs scan’), but even without that I like to keep
a copy of the static binaries around Just In Case. It would be nice
if Guix could take care of them.

The static versions are all suffixed with ‘.static’ by upstream, so
no collisions & no ugly renaming.

Together with the util-linux:static dependency, this adds some 18 (!)
MiB of binaries—but unless I'm horribly mistaken they should never be
installed by default, right? The overhead in build time is negligible.

Kind regards,

T G-R