fix(@angular/build): cleanup karma temporary directory after process … #2081

Job	Run time
build-e2e-windows	23s
build	23s
lint	2m 20s
test	0s
publish-snapshots	0s
Browser Compatibility Tests	0s
e2e	0s
e2e-package-managers	0s
e2e-snapshots	0s
e2e-windows	0s
	3m 6s

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