[seL4] Error while building in docker

This morning I saw this error when building sel4:

/bin/sh: 1: PROTOBUF_PROTOC_EXECUTABLE-NOTFOUND: not found

I noticed a warning when starting the docker container about trustworthysystems/camkes:latest being over 30 days old. I thought that using an up to date pull of:

https://github.com/SEL4PROJ/seL4-CAmkES-L4v-dockerfiles.git

would keep the build env up to date but that apparently is either not the case or there is a problem with the repo.

I ran:

docker pull trustworthysystems/camkes

and the warning was resolved and I could build seL4. Is pulling that docker image supposed to be necessary?

Thanks!