Use chaining for custom .targets #6218

Job	Run time
build-packages	4m 11s
build-solution (Debug, x64)	6m 52s
build-solution (Debug, arm64)	7m 28s
build-solution (Release, x64)	8m 17s
build-solution (Release, arm64)	6m 56s
verify-packages	6m 52s
run-samples	3m 34s
run-tests	7m 31s
run-samples-aot (x64)	10m 26s
run-tests-d3d12ma	5m 25s
run-samples-aot (arm64)	7m 14s
run-tests-win2d	5m 32s
publish-nightlies-github	19s
publish-nightlies-azure-devops	43s
	1h 21m 20s

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