Add glibc runtime action (14/24)

[MikeMcQuaid]

Three glibc-family formulae share locale generation and timezone-link
setup with different rules for the legacy variants.

• derive requested locales while always providing the UTF-8 default
• invoke the installed localedef with normalised charmaps
• preserve host timezone links when their sources exist

AI disclosure: using OpenAI Codex 5.6 Sol max with local review and
testing.

[Copilot]

Pull request overview

Adds a new install-steps “formula action” to configure glibc-family runtime state (locale generation and timezone link setup), and wires it into the install steps DSL, runner dispatch, RuboCop auditing, tests, and documentation.

Changes:

• Introduces configure_glibc_runtime as an install-step DSL action and adds runner support (run_configure_glibc_runtime).
• Extends RuboCop’s allowed install-step method list and updates related RuboCop specs.
• Adds a dispatch spec for the new action and documents the repeated action in the Formula Cookbook.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
Library/Homebrew/test/rubocops/install_steps_spec.rb	Updates RuboCop cop specs to include the new DSL action in allowed methods.
Library/Homebrew/test/install_steps_spec.rb	Adds a spec asserting runner dispatch for the new configure_glibc_runtime step.
Library/Homebrew/rubocops/shared/install_steps_helper.rb	Allows configure_glibc_runtime within post_install_steps blocks.
Library/Homebrew/install_steps/formula_actions.rb	Implements run_configure_glibc_runtime to generate locales and set timezone-related symlinks.
Library/Homebrew/install_steps.rb	Adds DSL method configure_glibc_runtime and runner dispatch case.
docs/Formula-Cookbook.md	Documents the new repeated action (but currently with a name mismatch).

Comments suppressed due to low confidence (2)

Library/Homebrew/install_steps/formula_actions.rb:114

• run_configure_glibc_runtime creates lib/locale but doesn’t ensure the parent directories for the timezone symlink targets exist. File.symlink will raise Errno::ENOENT if context_path("etc") or context_path("share") don’t already exist.

        [[Pathname("/etc/localtime"), context_path("etc")/"localtime"],
         [Pathname("/usr/share/zoneinfo"), context_path("share")/"zoneinfo"]].each do |source, target|
          File.symlink source, target if source.exist? && !target.exist?
        end

Library/Homebrew/install_steps/formula_actions.rb:105

• Charmap normalisation only handles the exact lowercase string "utf8". To reliably normalise common variants (e.g. "UTF8", "utf-8"), compare case-insensitively after removing dashes.

          if charmap.present?
            charmap = "UTF-8" if charmap == "utf8"
            run_command context_path("bin")/"localedef", "-i", lang, "-f", charmap, locale

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