CMP0189: Restore support for linking $<TARGET_PROPERTY:tgt,LINK_LIBRARIES>

In general we disallow references to transitive target properties, such
as `COMPILE_DEFINITIONS`, in `[INTERFACE_]LINK_LIBRARIES` properties,
because the latter establish the transitivity itself.  Prior to CMP0189,
the `[INTERFACE_]LINK_LIBRARIES` properties were not themselves transitive
in `$<TARGET_PROPERTY>` expressions, so existing projects have code like

    target_link_libraries(foo PRIVATE "$<TARGET_PROPERTY:tgt,LINK_LIBRARIES>")

Policy CMP0189's NEW behavior, introduced by commit b3da9c6d60 (GenEx:
Evaluate LINK_LIBRARIES target properties transitively, 2025-02-24,
v4.1.0-rc1~731^2), makes `$<TARGET_PROPERTY:tgt,LINK_LIBRARIES>`
transitive, causing the above to be rejected.  Since evaluation of a
target's link libraries can already encounter and handle other targets'
link libraries, allow it in this case.

Fixes: #27265

Source/cmGeneratorExpressionNode.cxx

@@ -2903,7 +2903,8 @@ static const struct TargetPropertyNode : public cmGeneratorExpressionNode
           dagCheckerParent->EvaluatingLinkerLauncher()) {
         // No check required.
       } else if (evaluatingLinkLibraries) {
-        if (!interfacePropertyName.empty()) {
+        if (!interfacePropertyName.empty() &&
+            interfacePropertyName != "INTERFACE_LINK_LIBRARIES"_s) {
           reportError(
             eval, content->GetOriginalExpression(),
             "$<TARGET_PROPERTY:...> expression in link libraries "

Tests/RunCMake/GenEx-TARGET_PROPERTY/LinkLikewise-CMP0189-NEW.cmake

@@ -0,0 +1,5 @@
+cmake_policy(SET CMP0189 NEW)
+include(LinkLikewise-common.cmake)
+
+# Test that CMP0189 NEW tolerates circular LINK_LIBRARIES references.
+target_link_libraries(main1 PRIVATE "$<TARGET_PROPERTY:main2,LINK_LIBRARIES>")

Tests/RunCMake/GenEx-TARGET_PROPERTY/LinkLikewise-CMP0189-OLD.cmake

@@ -0,0 +1,2 @@
+cmake_policy(SET CMP0189 OLD)
+include(LinkLikewise-common.cmake)

Tests/RunCMake/GenEx-TARGET_PROPERTY/LinkLikewise-common.cmake

@@ -0,0 +1,12 @@
+enable_language(C)
+
+add_library(foo STATIC LinkLikewiseLib.c)
+
+add_executable(main1 LinkLikewiseMain.c)
+add_executable(main2 LinkLikewiseMain.c)
+
+# main1 depends on foo.
+target_link_libraries(main1 PRIVATE foo)
+
+# main2 depends on foo, but express it by referencing main1's dependency.
+target_link_libraries(main2 PRIVATE "$<TARGET_PROPERTY:main1,LINK_LIBRARIES>")

Tests/RunCMake/GenEx-TARGET_PROPERTY/LinkLikewiseLib.c

@@ -0,0 +1,4 @@
+int LinkLikewiseLib(void)
+{
+  return 0;
+}

Tests/RunCMake/GenEx-TARGET_PROPERTY/LinkLikewiseMain.c

@@ -0,0 +1,5 @@
+extern int LinkLikewiseLib(void);
+int main(void)
+{
+  return LinkLikewiseLib();
+}

Tests/RunCMake/GenEx-TARGET_PROPERTY/RunCMakeTest.cmake

@@ -17,6 +17,15 @@ run_cmake(TransitiveLink-CMP0166-OLD)
 run_cmake(TransitiveLink-CMP0166-NEW)
 run_cmake(Unset)
 
+function(run_LinkLikewise case)
+  run_cmake(LinkLikewise-${case})
+  set(RunCMake_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/LinkLikewise-${case}-build)
+  set(RunCMake_TEST_NO_CLEAN 1)
+  run_cmake_command(LinkLikewise-${case}-build ${CMAKE_COMMAND} --build . --config Debug)
+endfunction()
+run_LinkLikewise(CMP0189-OLD)
+run_LinkLikewise(CMP0189-NEW)
+
 block()
   run_cmake(Scope)
   set(RunCMake_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/Scope-build)