package-release.sh: Fix format of archives.

Ensure that the .tar.bz2 archives actually use bzip2 compression!

This fixes a small typo that ended up preventing compressed archive
generation. After this patch, a typical Darwin binaries archive
changes from 21 to 8 MB!

Change-Id: I44505db981916e82360098e3c98d4675a83806d8
1 file changed