In the extensible SDK we force NATIVELSBSTRING to "SDK-Fixed"; however uninative.bbclass is already setting it to "universal" so we don't need to do that. We may as well drop the code forcing the value and change the code that prepares the sstate files for the ext SDK to use "universal" instead.
Fix merged to master: http://git.yoctoproject.org/cgit/cgit.cgi/poky/commit/?id=a4f496ae43d6c2698050d79b1f010cbc30ef901d