This adds a possibility to specify --diff option to idf.py size,
size-components and size-files commands. This can be map file directly,
project directory or build directory.
Usage example:
idf.py size-components --diff ../hello_world2/build/hello_world.map
idf.py size-components --diff ../hello_world2/build
idf.py size-components --diff ../hello_world2
Signed-off-by: Frantisek Hrbata <frantisek.hrbata@espressif.com>