fix(@angular/build): prevent stripping nested sourceMappingURL comments #10692

Job	Run time
build-e2e-windows	51s
lint	1m 6s
build	1m 5s
e2e-windows	1s
Browser Compatibility Tests	1s
publish-snapshots	1s
test	1s
e2e-package-managers	1s
e2e	1s
e2e-snapshots	1s
	3m 9s

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