Only apply standard swift settings on valid targets #113

Job	Run time
Unit tests / Construct unit test matrix	4s
Integration test / Windows (6.0)	3s
Integration test / Windows (nightly-6.1)	1s
Integration test / Linux (5.9)	19s
Integration test / Windows (nightly-main)	2s
Integration test / Linux (5.10)	19s
Soundness / API breakage check	19s
Integration test / Linux (6.0)	19s
Soundness / Broken symlinks check	2s
Soundness / Documentation check	18s
Soundness / Format check	19s
Integration test / Linux (nightly-6.1)	18s
Soundness / License headers check	4s
Soundness / Unacceptable language check	2s
Integration test / Linux (nightly-main)	19s
Soundness / Python lint check	5s
Soundness / Shell check	18s
Soundness / YAML lint check	5s
Unit tests / Unit tests / Linux (5.9)	23s
Unit tests / Unit tests / Linux (5.10)	26s
Unit tests / Unit tests / Linux (6.0)	27s
Unit tests / Unit tests / Linux (nightly-next)	29s
Unit tests / Unit tests / Linux (nightly-main)	30s
	5m 31s

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