Provide native builds for M1 Apple Silicon (ARM) Macs in Homebrew

[grahamrb]

AdoptOpenJDK now includes a build for the new M1-based (Apple Silicon) Macs. Ideally, the Homebrew package should provide this ARM based build when being installed on an Apple Silicon Mac rather than relying on Rosetta 2 to run the JDK.

Link to relevant AdoptOpenJDK ticket where ARM builds have been implemented: https://github.com/adoptium/temurin-build/issues/1922

Current output when running brew install --cask adoptopenjdk on an M1 Mac without Rosetta 2 installed:

installer: This package requires Rosetta 2 to be installed.
                Please install Rosetta 2 and then try again.
                    `sudo softwareupdate --install-rosetta`

installer: Error - AdoptOpenJDK can’t be installed on this computer.