Roll tarballs slightly differently so we actually get compression.

We were relying on "git archive" being able to create tar.gz files,
but that ability isn't present in the git that comes with CentOS 6,
so we use git to create a tar file and then compress it ourselves.

make_release

@@ -28,7 +28,7 @@ do_tar ()
 {
     tarball=${dirname}.tar.gz
     rm -f ${tarball}
-    git archive --prefix ${dirname}/ ${tag} -o ${tarball}
+    git archive --format=tar --prefix ${dirname}/ ${tag} | gzip -9 > ${tarball}
 
     # Compute SHA256 hash
     case `uname -s` in