Build command does not expose github-artifacts-* workflow flags

[KickNext]

Current flutterpi_tool build does not accept the workflow-artifact flags that the lower cache plumbing already supports.

Repro on current main:

flutterpi_tool build \
  --release \
  --arch arm64 \
  --cpu generic \
  --github-artifacts-runid=23382732417 \
  --github-artifacts-engine-version=052f31d115eceda8cbff1b3481fcde4330c4ae12

Result:

Could not find an option named "--github-artifacts-runid".

Relevant detail: FlutterpiCommandMixin.createCustomCache() already knows about:

• github-artifacts-repo
• github-artifacts-runid
• github-artifacts-engine-version
• github-artifacts-auth-token

But BuildCommand does not currently expose those options, so that path is unreachable from the CLI.

This matters for latest-Flutter build workflows where the required engine artifacts are only available from a specific workflow run.

[WinXaito]

It would be great to have a way to pin artifact. It allows for reproductible build and reduce supply chain risks.

I would even prefer to have a way to download manually (for CI) the artifacts, so I can verify file checksum and use a --offline argument. So flutterpi_tool will not download anything.