snort3: enable more control over the process

@graysky2

Hi

When I was playing around with my snort3, I realized that it lacks some useful functionality to control the running process.
They are:

• by providing --shell CLI option, Snort will be able to get commands, execute them and respond back to the user's console; it is useful for manual debuggiong and adjusting snort configurations
• by providing --control-socket <file> CLI option will create a UNIX-scoket, which will be served by the running process, performing the same role as the option above; it could be useful for GUI or other backend scripts to control the running engine

Could you add the following option to Makefile?

CMAKE_OPTIONS += -DENABLE_SHELL

You might want to try the command below to get the idea (look at 'remote commands' section)
snort --help-module snort
(Some other modules support remote commands as well)

One of the noteable ability is reloading new configuration on-the-fly and dumping actual packet and module statistics.

Locate the Snort3 package Makefile and inspect how its CMAKE_OPTIONS are passed to the build. Run snort --help-module snort to review the remote commands, then verify that enabling -DENABLE_SHELL produces the requested shell support in the built package.