Only apply standard swift settings on valid targets #58

Job	Run time
Construct Cxx interop matrix	4s
Unit tests / Unit tests (5.9)	3m 57s
Unit tests / Unit tests (5.10)	3m 58s
Unit tests / Unit tests (6.0)	4m 20s
Unit tests / Unit tests (nightly-6.1)	2m 54s
Unit tests / Unit tests (nightly-main)	2m 53s
Soundness / Unacceptable language check	5s
Soundness / Documentation check	1m 46s
Soundness / API breakage check	2m 11s
Soundness / Broken symlinks check	4s
Soundness / Format check	35s
Soundness / License headers check	7s
Soundness / Python lint check	8s
Soundness / Shell check	37s
Soundness / YAML lint check	4s
Cxx interop / Linux (5.9)	1m 24s
Cxx interop / Linux (5.10)	1m 18s
Cxx interop / Linux (6.0)	1m 36s
Cxx interop / Linux (nightly-next)	1m 49s
Cxx interop / Linux (nightly-main)	1m 48s
	31m 38s

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