Ensure functions start with clean CFA state.

.cfi_startproc doesn't reset CFA state and so delivering exceptions and the
like can leave the CFA with an incorrect offset. Reset the state in the
DEFINE_FUNCTION macro.
Also fix using test/run-test with --gdb for the target.

Change-Id: I4c03768e118ef1e06d34fedce856919e6ecba0c4