Add -N/--artifact-name argument to parser to name libraries

[theotherjimmy]

Only makes sence for --source builds (which only work with --build)

[theotherjimmy]

cc @screamerbg

[screamerbg]

Thanks @theotherjimmy

[jenia81]

@screamerbg @theotherjimmy
I don't see that this option was exported to "mbed compile" options.
Currently, I am working with mbed-cli 0.7.3 version and I don't see that I can compile a library with -N/--artifact-name option.
I do see the change in build.py.
Am I missing something?