Note
A call to target_link_libraries(<target> ...) may update this
property on <target>. If <target> was not created in the same
directory as the call then target_link_libraries() will wrap each
entry with the form ::@(directory-id);...;::@, where the ::@ is
literal and the (directory-id) is unspecified.
This tells the generators that the named libraries must be looked up in
the scope of the caller rather than in the scope in which the
<target> was created. Valid directory ids are stripped on export
by the install(EXPORT) and export() commands.