Don't destroy build files before recreating
Don't destroy build files before recreating

The vendored boostrap files not making building more compuationally
expensive. Therefore the `build` directory should not be wiped before
recreating it. Middlemanapp can handle updating only the changed files.

Signed-off-by: Michael Barton <1d6e1cf70ec6f9ab28d3ea4b27a49a77654d370e@michaelbarton.me.uk>

bioboxes/bioboxes.org,bioboxes/bioboxes.org,bioboxes/bioboxes.org,bioboxes/bioboxes.org