Preliminary support for macOS 27

### `brew doctor` output ```shell Please note that these warnings are just used to help the Homebrew maintainers with debugging if you file an issue. If everything you use Homebrew for is working fine: please don't worry or file an issue; just ignore this. Thanks! Warning: You are using macOS 27. We do not provide support for this pre-release version. This is a Tier 2 configuration: https://docs.brew.sh/Support-Tiers#tier-2 You can report issues with Tier 2 configurations to Homebrew/* repositories! Read the above document before opening any issues or PRs. Homebrew will ignore formulae, casks and commands from these taps when `HOMEBREW_REQUIRE_TAP_TRUST` is set. This will become the default in Homebrew 6.0.0 or 5.2.0, whichever comes first. Enable trust checks now with: export HOMEBREW_REQUIRE_TAP_TRUST=1 Trust specific formulae, casks or commands with: brew trust --formula <user>/<tap>/<formula> brew trust --cask <user>/<tap>/<cask> brew trust --command <user>/<tap>/<command> or trust installed formulae from these taps with: brew trust --formula protonpass/tap/pass-cli You can trust all formulae, casks and commands from these taps with: brew trust protonpass/tap Prefer trusting only the specific formulae, casks or commands you need. Untap them with: brew untap protonpass/tap To keep allowing them by default during the transition: export HOMEBREW_NO_REQUIRE_TAP_TRUST=1 This is not recommended and will be removed in a later release. ``` ### Verification - [x] I ran `brew update` twice and am still able to reproduce my issue. - [x] My "`brew doctor` output" above says `Your system is ready to brew` or a definitely unrelated `Tier` message. - [x] This issue's title and/or description do not reference a single formula e.g. `brew install wget`. If they do, open an issue at https://github.com/Homebrew/homebrew-core/issues/new/choose instead. ### `brew config` output ```shell HOMEBREW_VERSION: 5.1.15 ORIGIN: https://github.com/Homebrew/brew HEAD: 863696a47f8d9292cb25084b6f8228e003084101 Last commit: 6 days ago Branch: stable Core tap JSON: 08 Jun 23:11 UTC Core cask tap JSON: 08 Jun 23:11 UTC HOMEBREW_PREFIX: /opt/homebrew HOMEBREW_CASK_OPTS: [] HOMEBREW_DOWNLOAD_CONCURRENCY: 32 HOMEBREW_FORBID_PACKAGES_FROM_PATHS: set HOMEBREW_MAKE_JOBS: 16 Homebrew Ruby: 4.0.5 => /opt/homebrew/Library/Homebrew/vendor/portable-ruby/4.0.5_1/bin/ruby CPU: 16-core 64-bit arm_brava Clang: 21.0.0 build 2100 Git: 2.54.0 => /Applications/Xcode.app/Contents/Developer/usr/bin/git Curl: 8.7.1 => /usr/bin/curl macOS: 27.0-arm64 CLT: 27.0.0.0.1780650213 Xcode: 27.0 Metal Toolchain: N/A Rosetta 2: false ``` ### What were you trying to do (and why)? Upgrade Homebrew packages. ### What happened (include all command output)? `Error: unknown or unsupported macOS version: :dunno` ### What did you expect to happen? The update should happen successfully. ### Step-by-step reproduction instructions (by running `brew` commands) ```shell Step 1: run "brew upgrade" ```