Xamarin Studio 5.9 + F# - Target _CreateNativeLibraryArchive failing

If you're seeing an error like this in Xamarin Studio 5.9, building an Android project:

Target _CreateNativeLibraryArchive:
/Library/Frameworks/Mono.framework/External/xbuild/Xamarin/Android/Xamarin.Android.Common.targets:
error : Error executing task CreateNativeLibraryArchive: Argument cannot be
null.
Parameter name: unformatted
Build FAILED.

You may have mips binary files marked as EmbeddedNativeLibrary.  Turn that off (mips isn't supported yet anyway), and you should be able to build.

The bug has been reported to Xamarin - tech support found the solution.