Unity: Proper handling of object libraries

Fixes: #20051

Source/cmGlobalGenerator.cxx

@@ -1567,6 +1567,15 @@ bool cmGlobalGenerator::AddAutomaticSources()
       lg->AddPchDependencies(gt);
     }
   }
+  // The above transformations may have changed the classification of sources.
+  // Clear the source list and classification cache (KindedSources) of all
+  // targets so that it will be recomputed correctly by the generators later
+  // now that the above transformations are done for all targets.
+  for (cmLocalGenerator* lg : this->LocalGenerators) {
+    for (cmGeneratorTarget* gt : lg->GetGeneratorTargets()) {
+      gt->ClearSourcesCache();
+    }
+  }
   return true;
 }
 

Source/cmLocalGenerator.cxx

@@ -2307,6 +2307,7 @@ void cmLocalGenerator::AddPchDependencies(cmGeneratorTarget* target)
   }
   const std::string buildType = cmSystemTools::UpperCase(config);
 
+  // FIXME: Refactor collection of sources to not evaluate object libraries.
   std::vector<cmSourceFile*> sources;
   target->GetSourceFiles(sources, buildType);
 
@@ -2469,6 +2470,7 @@ void cmLocalGenerator::AddUnityBuild(cmGeneratorTarget* target)
     cmStrCat(this->GetCurrentBinaryDirectory(), "/CMakeFiles/",
              target->GetName(), ".dir/Unity/");
 
+  // FIXME: Refactor collection of sources to not evaluate object libraries.
   std::vector<cmSourceFile*> sources;
   target->GetSourceFiles(sources, buildType);