Move BUILD into a subdirectory

# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
#
# Author:    John Doe <john@foo.com>
# Date:      Fri Dec 29 18:36:06 2017 -0500
#
# On branch master
# Changes to be committed:
#	renamed:    BUILD -> gdir/BUILD
#
