DRTVWR-494: Show copy-paste-friendly env vars and test command.

Moderately often I want to copy the (long) integration test program path from
build output and rerun the test program by hand. But typically we need
environment variables set as well so it can find its dynamic libraries. This
has resulted in my copying parts of several lines of build output, then
pasting to a command prompt, then hand-tweaking the pasted text so it makes
sense as a command.

Streamline run_build_test.py output so less hand-tweaking is needed.