Matrix jobs only start when specifying exactly built-in as label to select the built-in node.

When using a label expression like "built-in || master" or a different label that is configured for the built-in node, the matrix job will stay in the queue forever.

This used to work fine with Jenkins 2.264.3.

Note: the matrix jobs WILL start fine with a label or label expression that resolves e.g. to a docker cloud instead of the built-in node.