Clarification on pull request #42

[malus-brandywine]

Additional docker image makes updates of packages according to build instruction Developer system requirements.
The only change is: "make user_cp" instead of "make user".

Instruction to build SDK would be:

Run container as recommended here: Using Docker for seL4, etc

Inside the container run:

/tmp/cp_prep.sh

The script will install proper sources of Core Platform and seL4 as well as
create python environment inside /host/sel4-core-platform

cd /host/sel4-core-platform/sel4cp
../pyenv/bin/python build_sdk.py --sel4=../sel4_cp_support