Add workflow_call trigger to build workflow

[lorengordon]

Changes offered/proposed in this pull request:

• Add a workflow_call trigger to build.yml, mirroring the existing workflow_dispatch inputs, so other repos (e.g. amigen9) can invoke this build workflow as a reusable workflow.

This is Phase A of enabling amigen9 to run ephemeral CI builds by calling into this workflow. No other jobs change: the trigger job's "Set spel inputs" step already reads ${{ inputs.* }} generically regardless of trigger type, and the release-pr job stays gated on schedule or inputs.SPEL_RELEASE.

[lorengordon]

/build

[Copilot]

Copilot review overview

🟡 Changes recommended

The added github.event_name == 'workflow_call' condition never evaluates true in a reusable workflow, so the change does not reliably run the build when called as intended.

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Review effort: Balanced
Findings: 1 · 1

Open (2)

• workflow_call check never matches in reusable workflow · New
• Reusable workflow inputs omit some documented dispatch values · New

What changed in this PR

This PR adds a workflow_call trigger to .github/workflows/build.yml so that the SPEL build workflow can be invoked as a reusable workflow from other repositories (e.g. amigen9). It declares a workflow_call.inputs block that reuses the SPEL build parameters and extends the trigger job's if condition to include workflow_call. This is described as Phase A of enabling amigen9 to run ephemeral CI builds against this workflow.

Changes:

• Add a workflow_call trigger with an inputs block covering a subset of the existing workflow_dispatch inputs.
• Add github.event_name == 'workflow_call' to the trigger job's if gate.

File	Description
.github/​workflows/​build.yml	Adds workflow_call trigger inputs and extends the trigger job's if condition to attempt to run for reusable-workflow invocations

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[Copilot]

Copilot review overview

🔵 Needs a closer look

Exposing the build workflow as a cross-repo reusable workflow whose gating depends on caller-controlled event context carries security and operational implications that warrant human review.

Review effort: Balanced
Findings: 1

Open (1)

• Clarify that reusable inputs are an intentional subset · New

Resolved since last review (2)

• workflow_call check never matches in reusable workflow
• Reusable workflow inputs omit some documented dispatch values

[mergify]

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