perf(@angular/build): dispose builder result context early in non-wat… #3818

Job	Run time
list	44s
workflow (devkit-core-tests-rerun)	1m 52s
workflow (devkit-core-tests)	1m 55s
workflow (build-cli)	1m 41s
workflow (modules-builder-tests)	2m 5s
workflow (build-unit-tests)	2m 31s
	10m 48s

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