Except if the runaway code falls into another piece of program with WD reset. :P (these reset chunks often must be scattered in quite a few places of the memory to keep your program running...) I'd prefer if it had, say, a "recently reset" flag that stays lit for a few cycles after reset.
i.e.

;blah blah
WDRST1:
MOV	WDTRST,#0x1E
MOV	WDTRST,#0xE1
JNB	WDRECENT,WDRST1

If interrupt happens during the reset, the watchdog won't be reset until interrupt ends, WDRECENT remains low, as watchdog hasn't been reset recently. If the three above instructions happen in a row, WDRECENT will be set to 1 for long enough to pass JNB.