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
diff --git a/distrib/package-release.sh b/distrib/package-release.sh
index a766937..0d1a841 100755
--- a/distrib/package-release.sh
+++ b/distrib/package-release.sh
@@ -506,7 +506,7 @@
 
     dump "[$PKG_NAME] Creating tarball."
     PKG_FILE=$PKG_DIR/$PKG_PREFIX-$PKG_REVISION-$SYSTEM.tar.bz2
-    (run cd "$TEMP_BUILD_DIR"/$SYSTEM && run tar cf $PKG_FILE $PKG_PREFIX-$PKG_REVISION)
+    (run cd "$TEMP_BUILD_DIR"/$SYSTEM && run tar cjf $PKG_FILE $PKG_PREFIX-$PKG_REVISION)
 done
 if [ "$OPT_COPY_PREBUILTS" ]; then
     for SYSTEM in linux darwin; do