Revert "target_link_libraries: Allow use with targets in other directories"

Revert commit v3.12.0-rc1~82^2 (target_link_libraries: Allow use with
targets in other directories, 2018-05-11).  The RHS target scoping and
visibility rules are not clear and will need further investigation
before the feature can be added.

Issue: #17943
42 jobs for revert-subdirectory-linking
Status Name Job ID Coverage
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