Workaround for a linux kernel bug which affects the krait cpu - https://lkml.org/lkml/2013/10/25/3

By wrapping sigaction we make sure to always install a signal handler compiled for thumb.
The source code for the signal handler can be found here:
https://github.com/Unity-Technologies/krait-signal-handler
clone and build krait-signal-handler as part of the build process