[JustMaris]

Homebrew deprecated Ruby postflight blocks in casks (brew warns on every eraser install/upgrade). GoReleaser's hooks.post.install always renders one, so the step moves to custom_block as a postflight_steps block.

• chdir: "." resolves to the staged path; {{staged_path}} can't be used because GoReleaser templates custom_block.
• Verified locally: GoReleaser snapshot renders the block; reinstalling the cask with it gives no deprecation warning, the quarantine attribute is present before the step and gone after, and eraser --version runs.
• custom_block lands at the top of the cask, so brew style flags stanza order (cosmetic; the tap CI only runs on PRs and the current cask already fails style on the deprecation).