fix: use non-deprecated postflight_steps for cask quarantine removal

[joaofsantos]

Summary

brew install/upgrade/untap for the go-task cask currently prints:

Warning: Calling `postflight` is deprecated! Use `postflight_steps` instead.
Please report this issue to the go-task/homebrew-tap tap (not Homebrew/* repositories), or even better, submit a PR to fix it:
  .../go-task/homebrew-tap/Casks/go-task.rb:40

Homebrew's docs page linked from this repo's own .goreleaser.yml comment (https://goreleaser.com/customization/homebrew_casks/) still shows the deprecated postflight pattern this repo currently uses for quarantine removal, but the underlying postflight stanza itself is now deprecated in favor of postflight_steps.

I opened goreleaser/goreleaser#7156 to add an opt-in hooks.use_steps option to GoReleaser (needed because the new _steps stanzas use a restricted declarative DSL, not arbitrary Ruby, so it can't be a silent default-on switch). This PR switches .goreleaser.yml to use it once available, and rewrites the quarantine hook for the new DSL:

     hooks:
+      use_steps: true
       post:
         install: |
-          if system_command("/usr/bin/xattr", args: ["-h"]).exit_status == 0
-            system_command "/usr/bin/xattr", args: ["-dr", "com.apple.quarantine", "#{staged_path}/task"]
+          on_macos do
+            run "/usr/bin/xattr", args: ["-dr", "com.apple.quarantine", "{{staged_path}}/task"]
           end

on_macos do ... end replaces the old /usr/bin/xattr -h existence check as the guard for skipping this on Linux builds — same intent (this hook only makes sense on macOS), expressed in the new DSL's own idiom.

Verification

I couldn't run this repo's full release pipeline (needs a tagged build + goreleaser Pro fields already in .goreleaser.yml), but I did verify end-to-end that the generated cask content is valid, using a build of the goreleaser branch from #7156:

• Rendered this exact hook content through goreleaser's real cask-building pipeline (doBuildCask).
• Loaded the resulting postflight_steps block via a real Homebrew installation's Cask::CaskLoader.load — parses with zero deprecation warnings, correct postflight_steps → on_macos → run nesting.
• Validated .goreleaser.yml's homebrew_casks config (including this hook) against goreleaser's config schema via goreleaser check with the same patched build — no schema errors.

Status: draft, blocked on goreleaser/goreleaser#7156

This isn't mergeable yet — hooks.use_steps doesn't exist in any released GoReleaser version. Marking as draft until that PR lands and this repo's GoReleaser dependency is bumped to a version that includes it.

AI was used to help write this change (implementation and verification); I reviewed and verified it per the notes above.

🤖 Generated with Claude Code

[vmaerten]

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