Only apply standard swift settings on valid targets #24

Job	Run time
Cxx interop / Construct Cxx interop matrix	2s
Unit tests / Unit tests (5.9)	1m 20s
Unit tests / Unit tests (5.10)	1m 12s
Unit tests / Unit tests (6.0)	1m 29s
Unit tests / Unit tests (nightly-6.1)	1m 42s
Unit tests / Unit tests (nightly-main)	1m 39s
Soundness / API breakage check	1m 42s
Soundness / Documentation check	1m 31s
Soundness / License headers check	2s
Soundness / Unacceptable language check	3s
Soundness / Broken symlinks check	3s
Soundness / Format check	36s
Soundness / Python lint check	5s
Soundness / Shell check	37s
Soundness / YAML lint check	2s
Cxx interop / Cxx interop / Linux (5.9)	1m 10s
Cxx interop / Cxx interop / Linux (5.10)	1m 12s
Cxx interop / Cxx interop / Linux (6.0)	1m 20s
Cxx interop / Cxx interop / Linux (nightly-next)	1m 29s
Cxx interop / Cxx interop / Linux (nightly-main)	1m 36s
	18m 52s

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