LINK_LIBRARIES: Evaluate separately for linking and usage requirements

We evaluate `LINK_LIBRARIES` and `INTERFACE_LINK_LIBRARIES` for two purposes:

* Constructing the link line.
* Collecting usage requirements.

We evaluate `INTERFACE_LINK_LIBRARIES` separately for each purpose in
order to support the `$<LINK_ONLY:...>` generator expression used to
express private link dependencies of a static library.  Previously we
only evaluated `LINK_LIBRARIES` for linking, and used that result for
collecting usage requirements too.  Therefore `$<LINK_ONLY:...>` does
not work in `LINK_LIBRARIES`.

With the introduction of `INTERFACE_LINK_LIBRARIES_DIRECT`, evaluation
of `LINK_LIBRARIES` now needs to distinguish these two cases in order to
honor link dependencies encountered through `$<LINK_ONLY:...>` without
also exposing other usage requirements through private dependencies of a
static library.  Revise internal infrastructure to distinguish the two
cases when evaluating `LINK_LIBRARIES`.  Make the information available
in code paths for `INTERFACE_LINK_LIBRARIES_DIRECT` and `LINK_ONLY`.
Defer actually using the information to later commits.

Issue: #22496

1 files changed, 2 insertions, 2 deletions

diff --git a/Source/cmComputeTargetDepends.cxx b/Source/cmComputeTargetDepends.cxx
index ef89c8b..3ff16a4 100644
--- a/Source/cmComputeTargetDepends.cxx
+++ b/Source/cmComputeTargetDepends.cxx
@@ -218,8 +218,8 @@ void cmComputeTargetDepends::CollectTargetDepends(int depender_index)
       emitted.insert(cmLinkItem(depender, false, cmListFileBacktrace()));
       emitted.insert(cmLinkItem(depender, true, cmListFileBacktrace()));
 
-      if (cmLinkImplementation const* impl =
-            depender->GetLinkImplementation(it)) {
+      if (cmLinkImplementation const* impl = depender->GetLinkImplementation(
+            it, cmGeneratorTarget::LinkInterfaceFor::Link)) {
         for (cmLinkImplItem const& lib : impl->Libraries) {
           // Don't emit the same library twice for this target.
           if (emitted.insert(lib).second) {