Sledgehammer lsblk update for JSON output

[benagricola]

Updated versions of lsblk from metapackage util-linux contain the ability to produce JSON output of block devices which would be very useful for iterating over raw storage. Version 2.27 and above have this functionality.

I can only find community builds for 2.29, looks like it's used for rkt: https://cbs.centos.org/koji/buildinfo?buildID=15169

Any chance this can be pulled in during the sledgehammer build process?