Include native run in some tests to verify kernel behaviour

For some tests, it makes sense to do a native run of the test app to make sure that the behaviour expected from the kernel (or other external entities emulated by DR) is correct. E.g. in linux.sigaction we have asserts that check the expected errno from the rt_sigprocmask syscall in various error scenaiors. It'll be good to verify that the kernel's behaviour hasn't changed by running the test app natively too, before running it under DR.

If we don't do the native run, we cannot be sure if what DR is doing is correct (e.g. returning EINVAL instead of EFAULT)