test_bot fixes for portable formulae

[cho-m]

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test_bot/formulae: run nested test-bot in temporary dir

This provides a clean directory to test bottling so that previously built bottles don't cause "Unexpected bottle" errors

https://github.com/Homebrew/homebrew-core/actions/runs/29179553748/job/86656464924#step:4:1833

 ==> Running Formulae#run!
  Error: Unexpected bottle JSON: /github/home/bottles/portable-ruby--4.0.5_1.arm64_linux.bottle.json
  Error: Unexpected bottle tarball: /github/home/bottles/portable-ruby--4.0.5_1.arm64_linux.bottle.tar.gz

Mktemp#run should be similar to Dir.mktmpdir { Dir.chdir { ... } }. Could use latter if preferred (need to change directory so that Pathname.pwd runs in clean directory).

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test_bot/formulae_detect: exclude portable when testing default

This avoids trying to rebuild portable formulae again within the nested test-bot run which may the cause of stalled runs

[Copilot]

Pull request overview

This PR adjusts Homebrew’s test_bot behavior around portable formulae to reduce flaky/stalled CI runs: it runs a nested brew test-bot in a clean temporary working directory to avoid “Unexpected bottle” artifacts, and it prevents portable formulae from being selected when running --test-default-formula.

Changes:

• Run the nested brew test-bot --test-default-formula inside an Mktemp directory to isolate bottle artifacts.
• When --test-default-formula is used, filter out portable-* formulae from the detected added/modified sets to avoid rebuilding them in that run.

Reviewed changes

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

File	Description
Library/Homebrew/test_bot/formulae.rb	Wrap nested brew test-bot invocation in Mktemp to run in a clean temporary directory.
Library/Homebrew/test_bot/formulae_detect.rb	Exclude portable-* formulae from detection when --test-default-formula is enabled.

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