Touch-ups related to versioning and master-build-script.sh.

 * Move the build directory setup code into master-build-script.sh.

 * Move stdout/stderr logging into master-build-script.sh.

 * Change the versioning scheme from a date to a one-digit DIST_VERSION
   number, which is currently 1.
Adjust the final archiving step.

 * Make the entire build directory user-readable.

 * Use xz instead of bzip2, but only on Linux, because OS X doesn't seem
   to support xz.  On the x86_64 build, creating the xz archive took longer
   than bzip2 (74 minutes vs 28 minutes), but the file was smaller
   (1.1GB vs 1.77GB).  The smaller size is worth the extra time.
Output a SUCCESS message once the build is complete.