Target declaration refactor #1603

Job	Run time
Android (ubuntu-latest, aarch64-linux-android)	8m 22s
cargo-deny	1m 2s
Compiletest (windows-latest)	17m 57s
Difftest (ubuntu-latest)	12m 44s
Compiletest (ubuntu-latest)	7m 32s
Test (macOS-latest)	13m 30s
Test (ubuntu-latest)	11m 30s
Difftest (macOS-latest)	15m 8s
Compiletest (macOS-latest)	7m 7s
Lint	6m 41s
Difftest (windows-latest)	22m 25s
Test (windows-latest)	21m 36s
test_success	4s
	2h 25m 38s

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