Need help on generating opendistro-alerting zip using a modified version of opendistro-alerting

I am using alerting-kibana-plugin (https://github.com/opendistro-for-elasticsearch/alerting-kibana-plugin)
to generate opendistro-alerting-1.2.0.0.zip. How could I generate a custom alerting zip that will contain my enhancement changes made to alerting (https://github.com/opendistro-for-elasticsearch/alerting) instead of opendistro-alerting-1.2.0.0

Did you try the instructions on the build section?
I will try to use the branches of opendistro-1.2 to make sure to build it for those versions and follow the instructions on the build sections

opendistro-for-elasticsearch/alerting at opendistro-1.2 -> Build
opendistro-for-elasticsearch/alerting-kibana-plugin at opendistro-1.2 -> Build

Yes.
The setup section in alerting kibana plugin specifies
Download and install the appropriate Open Distro for Elasticsearch Alerting plugin.

How do I install specific alerting changes that I have made and package it into a zip file?