Look for omni.ja in the correct place.

TBB_EXT was a typo.

config/chroot_local-includes/usr/local/sbin/unsafe-browser

@@ -122,7 +122,7 @@ set_chroot_browser_name () {
         TOP=browser/chrome
         REST=${SHORT}/locale
     else
-        PACK="${CHROOT}/"${TBB_EXT}"/Browser/browser/omni.ja"
+        PACK="${CHROOT}/${TBB_INSTALL}/Browser/browser/omni.ja"
         TOP=chrome
         REST=en-US/locale
     fi