cmComputeLinkInformation: prepare Item consumers for `OBJECT` libraries
After b6659669 (cmComputeLinkInformation: track OBJECT
library
dependencies, 2023-07-22), introduced in !8645 (merged) as a fix for #25112 (closed),
OBJECT
libraries were tracked in a separate member to reduce the risk
of further regressions. This commit prepares consumers to handle
OBJECT
libraries once they start appearing as link items.