`make_gcc_arm` tool does not generate the embeddable blobs

[microbit-carlos]

Generating and building uvision projects also creates the .c and .py files with the blobs embedded, but this does not happen with make_gcc_arm.

I don't have IAR, so I cannot confirm if these files are generated with that project type or not.

[microbit-carlos]

In the meantime we have to manually run the scripts/generate_blobs.py file.

Is there a way to add a "post build" step to progen? If not I guess the README could be updated to include this info.