build-unit-test-docker: Add missing stdplus deps
build-unit-test-docker: Add missing stdplus deps

Change-Id: I70580c511b48c4e6d725bfe472a99043a16589b7
Signed-off-by: William A. Kennington III <30fff5198f4d10ca1117e5f3ec82f3b4b8900d81@google.com>

openbmc/openbmc-build-scripts,openbmc/openbmc-build-scripts