Add usage requirements to update direct link dependencies

Link line construction starts with `LINK_LIBRARIES` and appends
dependencies from the transitive closure of `INTERFACE_LINK_LIBRARIES`.
Only the entries of `LINK_LIBRARIES` are considered direct link
dependencies.  In some advanced use cases, particularly involving static
libraries and static plugins, usage requirements need to update the list
of direct link dependencies.  This may mean adding new items, removing
existing items, or both.

Add target properties to encode these usage requirements:

* INTERFACE_LINK_LIBRARIES_DIRECT
* INTERFACE_LINK_LIBRARIES_DIRECT_EXCLUDE

Fixes: #22496

1 files changed, 6 insertions, 0 deletions

diff --git a/Source/cmLinkItem.h b/Source/cmLinkItem.h
index e715659..262728b 100644
--- a/Source/cmLinkItem.h
+++ b/Source/cmLinkItem.h
@@ -70,6 +70,12 @@ struct cmLinkInterfaceLibraries
   // Object files listed in the interface.
   std::vector<cmLinkItem> Objects;
 
+  // Items to be included as if directly linked by the head target.
+  std::vector<cmLinkItem> HeadInclude;
+
+  // Items to be excluded from direct linking by the head target.
+  std::vector<cmLinkItem> HeadExclude;
+
   // Whether the list depends on a genex referencing the head target.
   bool HadHeadSensitiveCondition = false;