Exception when running BasicMicArray

[shuchitak]

The DUT .xe run as part of BasicMicArray test, at the end of the test, exits using exit(0). https://github.com/xmos/lib_mic_array/blob/develop/tests/signal/BasicMicArray/src/app.c#L163
This causes it to crash with the error

xrun: Program received signal ET_ILLEGAL_RESOURCE, Resource exception.
0x000818f8 in __free_threadlocal_timer ()

As a workaround, using _Exit(0) instead of exit(0) fixes it, but it should be fixed properly my making sure all threads exit before exiting the application.