both md5sum and variable substitutions such as ${BUILDSUM:0:8}

both md5sum and variable substitutions such as ${BUILDSUM:0:8}
are not available in FreeBSD.
For the time being, put in a workaround so we can build the system,
and wait for the result of the discussion on whether we can store
the md5 as a string rather than 4 ints (if so, we won't need more
complex tricks with awk or sed for splitting the md5).

1.4 will be fixed when we decide the issue.

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@89328 65c4cc65-6c06-0410-ace0-fbb531ad65f3