i#1701 port to Android: ensure our library code is compiled as Thumb
i#1701 port to Android: ensure our library code is compiled as Thumb

Adds an explicit -mthumb instead of just relying on compiler defaults, as
it turns out the Android toolchain defaults to ARM instead of Thumb.

Review-URL: https://codereview.appspot.com/255170043

code4bones/dynamorio,code4bones/dynamorio,bl4ckic3/dynamorio,AmesianX/dynamorio,daksunt/dynamorio,bl4ckic3/dynamorio,bl4ckic3/dynamorio,AmesianX/dynamorio,daksunt/dynamorio,daksunt/dynamorio,daksunt/dynamorio,AmesianX/dynamorio,code4bones/dynamorio,bl4ckic3/dynamorio,bl4ckic3/dynamorio,code4bones/dynamorio,daksunt/dynamorio,code4bones/dynamorio,AmesianX/dynamorio,AmesianX/dynamorio