Since SPI flash operations can not be performed when the stack is in
external RAM, we need to switch to a different stack when doing a
core dump to flash. This is achieved by a pair of longjmp's, one of
which is crafted manually to jump into a designated function with a
specific stack set up.
The cost of this feature is a bit of IRAM, plus the DRAM required for
the extra stack.
Closes AUD-1355
de662d5e11