build/tools: Remove outdated reference to sloccount

We moves sloccount into the scripts/ directory in:

    commit 9570acc2d3267a91bd17a7fe9a504159be14296e
    Author: Chris Cummins <chrisc.101@gmail.com>
    Date:   Wed Feb 12 13:18:11 2014 +0000

        Move sloccount from tools/ into scripts/