fix(@angular/build): allow custom runner configuration file for unit-… #2222

Job	Run time
list	32s
workflow (modules-builder-tests)	1m 52s
workflow (build-cli)	1m 40s
workflow (build-unit-tests)	2m 20s
workflow (devkit-core-tests)	1m 34s
workflow (devkit-core-tests-rerun)	1m 28s
	9m 26s

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