build.yml: case() expression for vcpkg_commit missing input fallback on PR triggers

[rustyconover]

Bug

The COMMUNITY_EXTENSION_VCPKG_COMMIT output in the prepare job of build.yml uses inputs.duckdb_version directly in the case() expression:

COMMUNITY_EXTENSION_VCPKG_COMMIT: ${{ case(inputs.duckdb_version == 'v1.5.0', steps.parse.outputs.COMMUNITY_EXTENSION_VCPKG_COMMIT == '' && '84bab45d415d22042bd0b9081aea57f362da3f35' || steps.parse.outputs.COMMUNITY_EXTENSION_VCPKG_COMMIT, steps.parse.outputs.COMMUNITY_EXTENSION_VCPKG_COMMIT == '' && 'ce613c41372b23b1f51333815feb3edd87ef8a8b' || steps.parse.outputs.COMMUNITY_EXTENSION_VCPKG_COMMIT) }}

However, inputs.duckdb_version is a workflow_dispatch input. On pull_request triggers it is empty/null, so inputs.duckdb_version == 'v1.5.0' evaluates to false.

Compare with how DUCKDB_VERSION is set a few lines below, which correctly applies a fallback:

DUCKDB_VERSION: ${{ inputs.duckdb_version || 'v1.5.0' }}

Impact

On pull request builds, the case() condition is always false, so the default (third argument) is returned: ce613c41372b23b1f51333815feb3edd87ef8a8b — which provides Arrow 19.0.1 instead of the intended 84bab45d415d22042bd0b9081aea57f362da3f35 which provides Arrow 21.0.0.

This causes build failures for extensions that depend on Arrow 21 APIs (e.g., arrow::ToStatus).

Example: #1492

Suggested fix

Add the || 'v1.5.0' fallback to match the pattern used elsewhere:

COMMUNITY_EXTENSION_VCPKG_COMMIT: ${{ case((inputs.duckdb_version || 'v1.5.0') == 'v1.5.0', ...