Hi,

The following task lists some of the changes that we had to make to enable TF-M to be built using ExternalProject_Add from Zephyr, as well as enabling the use of ninja for TF-M builds (which is often significantly faster than using classic makefiles): https://developer.trustedfirmware.org/T760

The ninja changes have been tested with:

$ cmake -GNinja -DPROJ_CONFIG=`readlink -f ../configs/ConfigDefault.cmake` -DTARGET_PLATFORM=LPC55S69 -DBL2=False -DCOMPILER=GNUARM .. $ ninja

The changes to imgtool.py resolve some platform issues when signing binaries, and add a convenience requirements.txt file that can be run in CI to ensure that all of the Python dependencies are met for this tool.

Any concerns or feedback on these are welcome, but I would be interested to hear any opinions on ninja which is often considerably faster out of the box when compiling (at least on Linux and native OS X, which is what I use for my builds).

Best regards, Kevin