environment variables:

DEBUG:: whether to initialise basic debugging features at load time. the value is irrelevant; the test is for whether the variable is defined.
DEBUG_WAIT:: whether to wait for a debugger to attach before executing `main`.

LOG_LEVEL:: minimum log level that will render to the logging stream. note that a given level may have been compiled out and may not be present, eg. DEBUG tends to only be present for debug builds.
BREAK_LEVEL:: minimum log level that will trigger a breakpoint

JOB_THREADS:: default number of threads to spin up for job queues.
JOB_DEPTH:: the default size of the pending work item queue for a job queue.