Unity Builds: Do not set SKIP_AUTOGEN to source files

Fixes: #21028

Source/cmLocalGenerator.cxx

@@ -2848,7 +2848,6 @@ inline void RegisterUnitySources(cmGeneratorTarget* target, cmSourceFile* sf,
 {
   target->AddSourceFileToUnityBatch(sf->ResolveFullPath());
   sf->SetProperty("UNITY_SOURCE_FILE", filename.c_str());
-  sf->SetProperty("SKIP_AUTOGEN", "ON");
 }
 
 inline void IncludeFileInUnitySources(cmGeneratedFileStream& unity_file,

Tests/QtAutogen/Tests.cmake

@@ -29,6 +29,7 @@ ADD_AUTOGEN_TEST(UicInterface QtAutoUicInterface)
 ADD_AUTOGEN_TEST(UicNoGui uicNoGui)
 ADD_AUTOGEN_TEST(UicOnly uicOnly)
 ADD_AUTOGEN_TEST(UicSkipSource)
+ADD_AUTOGEN_TEST(UnityMocSource)
 
 if(QT_TEST_ALLOW_QT_MACROS)
   ADD_AUTOGEN_TEST(MocCMP0071)

Tests/QtAutogen/UnityMocSource/CMakeLists.txt

@@ -0,0 +1,12 @@
+cmake_minimum_required(VERSION 3.16)
+project(UnityMocSource)
+include("../AutogenGuiTest.cmake")
+
+set(CMAKE_AUTOMOC ON)
+set(CMAKE_UNITY_BUILD ON)
+
+add_library(library library.cpp)
+target_link_libraries(library ${QT_LIBRARIES})
+
+add_executable(unityMocSource main.cpp)
+target_link_libraries(unityMocSource PRIVATE library)

Tests/QtAutogen/UnityMocSource/library.cpp

@@ -0,0 +1,6 @@
+#include <QObject>
+class Test : public QObject
+{
+  Q_OBJECT
+};
+#include "library.moc"

Tests/QtAutogen/UnityMocSource/main.cpp

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