must-gather is a tool based on openshift-must-gather to collect data from kubernetes to review and support it's overall state and health.
Data collection scripts are kept in ./collection-scripts. The content of that folder is placed in /usr/bin in the image. Also the required oc binary required in the must-gather can be found on Client tools for OKD.
It's recommend to run the must-gather using oc adm must-gather --image=quay.io/<repo>/kube-must-gather:latest. To obtain the oc binary, refer to Client tools for OKD.