Autogen: Fix Ninja Multi-Config dependency graph regression

In commit 5363bebc1e (Autogen: Fix compilation of unchanged source files,
2024-07-16, v3.31.0-rc1~328^2) we relied on Ninja Multi-Config dependency graph
optimizations from commit 7c39dabdbc (Autogen: AUTO*_EXECUTABLE: add support
for per-config values, 2023-10-18, v3.29.0-rc1~105^2~1).  However, those graph
optimizations are conditional on versions of Qt that enable
[`AUTOGEN_BETTER_GRAPH_MULTI_CONFIG`](https://codereview.qt-project.org/c/qt/qtbase/+/513648).

`UseBetterGraph` should be checked to add ui files to `timestampByproducts`.

Fixes: #26475

Source/cmQtAutoGenInitializer.cxx

@@ -1340,12 +1340,25 @@ bool cmQtAutoGenInitializer::InitAutogenTarget()
   }
 
   if (this->Uic.Enabled) {
-    // Make all ui_*.h files byproducts of the ${target}_autogen/timestamp
-    // custom command if the generation of depfile is enabled.
-    auto& byProducts = useDepfile ? timestampByproducts : autogenByproducts;
-    for (auto const& file : this->Uic.UiHeaders) {
-      this->AddGeneratedSource(file.first, this->Uic);
-      byProducts.push_back(file.second);
+    auto const useAdvancedUicGraph = [this]() -> bool {
+      if (this->MultiConfig && this->GlobalGen->IsNinja()) {
+        return this->UseBetterGraph;
+      }
+      return true;
+    }();
+    if (useAdvancedUicGraph) {
+      // Make all ui_*.h files byproducts of the ${target}_autogen/timestamp
+      // custom command if the generation of depfile is enabled.
+      auto& byProducts = useDepfile ? timestampByproducts : autogenByproducts;
+      for (auto const& file : this->Uic.UiHeaders) {
+        this->AddGeneratedSource(file.first, this->Uic);
+        byProducts.push_back(file.second);
+      }
+    } else {
+      for (auto const& file : this->Uic.UiHeaders) {
+        this->AddGeneratedSource(file.first, this->Uic);
+        autogenByproducts.push_back(file.second);
+      }
     }
   }
 

Tests/RunCMake/Autogen_6/RunCMakeTest.cmake

@@ -6,6 +6,7 @@ if (DEFINED with_qt_version)
     -Dwith_qt_version=${with_qt_version}
     "-DQt${with_qt_version}_DIR:PATH=${Qt${with_qt_version}_DIR}"
     "-DCMAKE_PREFIX_PATH:STRING=${CMAKE_PREFIX_PATH}"
+    "-DCMAKE_AUTOGEN_BETTER_GRAPH_MULTI_CONFIG=ON"
   )
   if (QtCore_VERSION VERSION_GREATER_EQUAL 5.15.0)
     macro(set_test_variables_for_unwanted_builds)