[TF-M] New build system with IAR

I've started looking at the new build system, and it looks like a nice improvement.

I have a problem, that likely has a simple solution, although I'm not sure which.

I've looked at the AN521 target, and the preload.cmake file is included very early from the root CMakeLists.txt

The first line of preload.cmake is: --- set(CMAKE_SYSTEM_PROCESSOR cortex-m33+nodsp) ---

For IAR that line should be: --- set(CMAKE_SYSTEM_PROCESSOR Cortex-M33.no_dsp) ---

I need to discriminate between the toolchains already there, but I haven't figured out what the best way would be to do that. Not much is setup at this moment in the run.

Ideas?

Thomas