so, there's three ways I can think of to solve this:

* make two applications: one bootloader that loads from non-octospi flash, sets up octospi flash, then boots into the second application
    * both use cortex-m-rt
    * the bootloader has one memory.x that ignores octospi and just uses flash
    * the app has a second memory.x that ignores flash and just uses octospi
* maaaaybe use the `pre_init` hook to set up the octospi, this could be complicated, and probably should be done in assembly
* fork cortex-m-rt, and make a custom version that does more complicated setup.