Now that mac os x stack-fixing bustage is fixed on mozilla-central, go back to using XPCOM_DEBUG_BREAK=stack
Now that mac os x stack-fixing bustage is fixed on mozilla-central, go back to using XPCOM_DEBUG_BREAK=stack

nth10sd/funfuzz,MozillaSecurity/funfuzz,nth10sd/funfuzz,nth10sd/funfuzz,MozillaSecurity/funfuzz,MozillaSecurity/funfuzz