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/cmComputeLinkDepends.cxx b/Source/cmComputeLinkDepends.cxx
index a4dc01b..8cbdcaa 100644
--- a/Source/cmComputeLinkDepends.cxx
+++ b/Source/cmComputeLinkDepends.cxx
@@ -677,8 +677,8 @@ void cmComputeLinkDepends::AddVarLinkEntries(int depender_index,
 void cmComputeLinkDepends::AddDirectLinkEntries()
 {
   // Add direct link dependencies in this configuration.
-  cmLinkImplementation const* impl =
-    this->Target->GetLinkImplementation(this->Config);
+  cmLinkImplementation const* impl = this->Target->GetLinkImplementation(
+    this->Config, cmGeneratorTarget::LinkInterfaceFor::Link);
   this->AddLinkEntries(-1, impl->Libraries);
   this->AddLinkObjects(impl->Objects);