build-unit-test-docker.sh: Bake heavily-used repos into Docker image

Introduce a handful of core OpenBMC packages and a new file into the
docker image, /root/.depcache, which contains a comma-separated list of
${PACKAGE}:${COMMIT_ID} pairs. The commit ID represents the HEAD of
https://github.com/openbmc/${PACKAGE} master. The way the Dockerfile
change is structured means that we will rebuild the image to use updated
packages whenever the upstream master changes.

This improves build times by allowing us to avoid building the core
dependencies for every CI run whilst still keeping the environment
up-to-date.

Tested: Ran run-unit-test-docker.sh, confirmed no regressions

Change-Id: I4e0e1a86ffc0a26107d328a3418d6afa27b8f375
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
1 file changed