Option `enable_semihosting` is not working

Thank you for this great project. I have been using it as part of the Zephyr project and it works great.

I am using ARM semihosting for my printf statements and for each debug session I type monitor arm semihosting enable. After getting sick of doing that I wanted to enable semihosting by default for my board. When looking at the pyOCD options documentation, I got the feeling that I needed to create the following config file to enable arm semihosting.

# Set to True to handle semihosting requests. Also see the semihost_console_type option. Default is False.
enable_semihosting: True

However with this config file the semihosting breakpoints were still not parsed. So I tried pyocd gdbserver -O enable_semihosting=true, which also didn't work. After trying lots of variations I finally found the following working command: pyocd gdbserver --semihosting.

My conclusion was that the options parsing doesn't work correctly for enable_semihosting.

Start with the options documentation and reproduce the issue using the YAML setting and pyocd gdbserver -O enable_semihosting=true, then compare that behavior with pyocd gdbserver --semihosting. Trace how these option forms are parsed and verify that enabling semihosting works consistently through the config file and command-line option.