chore(docker): add Finch build helper script

[claytonblythe]

Summary

Add utils/docker/build_finch.sh as a Finch equivalent of utils/docker/build.sh for local contributor workflows.

This script mirrors the existing Docker helper:

• same arguments: {--arm64,--amd64} {jammy,noble} <tag>
• same packaging step (pack_package.js -> playwright-core.tar.gz)
• same Dockerfiles (utils/docker/Dockerfile.jammy|noble)
• only runtime invocation differs (finch build vs docker build)

Why

Some contributor environments use Finch instead of Docker CLI.
This helper provides a minimal, explicit path to build the same local Playwright image with Finch.

Scope / Non-goals

• No change to published image pipeline
• No CI changes
• No user-facing docs changes
• No new dependencies

Validation (macOS arm64, Finch v1.15.1)

1) Script usage/help

$ ./utils/docker/build_finch.sh -h
usage: build_finch.sh {--arm64,--amd64} {jammy,noble} playwright:localbuild-noble
...

2) Noble build + runtime + Playwright docker marker

$ ./utils/docker/build_finch.sh --arm64 noble playwright:localbuild-noble
/Users/.../utils/docker/playwright-core.tar.gz
...
#9 naming to docker.io/library/playwright:localbuild-noble done
#9 unpacking to docker.io/library/playwright:localbuild-noble done
#9 DONE 0.0s

$ finch run --rm playwright:localbuild-noble /bin/bash -lc 'node -v && npm -v && cat /etc/os-release | head -n 2 && cat /ms-playwright/.docker-info'
v24.14.0
11.9.0
PRETTY_NAME="Ubuntu 24.04.4 LTS"
NAME="Ubuntu"
{
  "driverVersion": "1.59.0-next",
  "dockerImageName": "mcr.microsoft.com/playwright:v1.59.0-next-noble"
}

3) Jammy build + runtime + Playwright docker marker

$ ./utils/docker/build_finch.sh --arm64 jammy playwright:localbuild-jammy
/Users/.../utils/docker/playwright-core.tar.gz
...
#9 naming to docker.io/library/playwright:localbuild-jammy done
#9 unpacking to docker.io/library/playwright:localbuild-jammy done
#9 DONE 0.0s

$ finch run --rm playwright:localbuild-jammy /bin/bash -lc 'node -v && npm -v && cat /etc/os-release | head -n 2 && cat /ms-playwright/.docker-info'
v24.14.0
11.9.0
PRETTY_NAME="Ubuntu 22.04.5 LTS"
NAME="Ubuntu"
{
  "driverVersion": "1.59.0-next",
  "dockerImageName": "mcr.microsoft.com/playwright:v1.59.0-next-jammy"
}

[claytonblythe]

@microsoft-github-policy-service agree

[yury-s]

This can live somewhere outside of this repository. We have build.sh only because it is used by our automation and we don't have one for Finch.