setup(mac): add adoptopenjdk8 in install_prereqs.sh
setup(mac): add adoptopenjdk8 in install_prereqs.sh

It's a dependency of bazel but not installed automatically via `brew install bazel`
soonho-tri/dreal4,dreal/dreal4,soonho-tri/dreal4,soonho-tri/dreal4,dreal/dreal4,soonho-tri/dreal4,dreal/dreal4,dreal/dreal4