Fix build-release.sh for new .0 versions
Fix build-release.sh for new .0 versions

`brew bump-formula-pr` refuses to update versions like "2019.08.12" to
"4.18.0" because it thinks 2019 is a newer version than 4. So we have to
update the formula file manually using a sequence of `gsed`s.

hhvm/homebrew-hhvm,hhvm/homebrew-hhvm