Why does mtouch fail when using a 3rd-party obj-c lib with LLVM optimizing?

I've got a project where I am not able to use LLVM optimizing b开发者_高级运维ecause I'm binding to an obj-c lib. Is there something I need to do to get around this? i.e. change a build setting when building the obj-c lib? or additional mtouch arguments in my build configs?

Update: I created a stand-alone project that exhibits this behavior and in the build output I'm getting a lot of these:

/var/folders/XV/XVCgAKTfGEmAUQGlxdGm9E+++TU/-Tmp-/tmp679d4c1.tmp/monotouch-facebook.dll.6.s:5620:Rest of line ignored. 1st junk character valued 45 (-).

And a lot of these:

/var/folders/XV/XVCgAKTfGEmAUQGlxdGm9E+++TU/-Tmp-/tmp679d4c1.tmp/monotouch-facebook.dll.6.s:5625:Can't relocate expression. Absolute 0 assumed.

And by a lot, I mean, like 80 of them. Each.

Turns out that I was using a 3rd party lib with THUMB turned on. You'll need to rebuild the lib with it turned off.