QtAutogen: Always run autogen step even when rcc is enabled (#15608)

In commit v3.2.0-rc1~480^2 (QtAutogen: Regenerate qrc files if their input
changes, 2014-09-17) the "cmake -E cmake_autogen" rule was switched from
always running to running as a custom command with dependencies if rcc
is enabled.  This is not correct because automoc always needs to re-run.
Switch back to always running the command.

Source/cmQtAutoGenerators.cxx

@@ -466,31 +466,11 @@ bool cmQtAutoGenerators::InitializeAutogenTarget(cmTarget* target)
   else
 #endif
     {
-    cmTarget* autogenTarget = 0;
-    if (!rcc_output.empty() && !isNinja)
-      {
-      std::vector<std::string> no_byproducts;
-      makefile->AddCustomCommandToOutput(rcc_output, no_byproducts,
-                                         depends, "",
-                                         commandLines, 0,
-                                         workingDirectory.c_str(),
-                                         false, false);
-
-      cmCustomCommandLines no_commands;
-      autogenTarget = makefile->AddUtilityCommand(
-                          autogenTargetName, true,
-                          workingDirectory.c_str(), rcc_output,
-                          no_commands, false, autogenComment.c_str());
-
-      }
-    else
-      {
-      autogenTarget = makefile->AddUtilityCommand(
+    cmTarget* autogenTarget = makefile->AddUtilityCommand(
                                 autogenTargetName, true,
                                 workingDirectory.c_str(),
                                 /*byproducts=*/rcc_output, depends,
                                 commandLines, false, autogenComment.c_str());
-      }
 
     // Set target folder
     const char* autogenFolder = makefile->GetState()

Tests/QtAutogen/CMakeLists.txt

@@ -167,3 +167,26 @@ file(TIMESTAMP "${qrc_file1}" file1_step1 "${timeformat}")
 if (NOT file1_step1 GREATER file1_before)
   message(SEND_ERROR "file1 (${qrc_file1}) should have changed in the first step!")
 endif()
+
+#-----------------------------------------------------------------------------
+try_compile(MOC_RERUN
+  "${CMAKE_CURRENT_BINARY_DIR}/automoc_rerun"
+  "${CMAKE_CURRENT_SOURCE_DIR}/automoc_rerun"
+  automoc_rerun
+  CMAKE_FLAGS "-DQT_QMAKE_EXECUTABLE:FILEPATH=${QT_QMAKE_EXECUTABLE}" "-DQT_TEST_VERSION=${QT_TEST_VERSION}"
+              "-DCMAKE_PREFIX_PATH=${Qt_PREFIX_DIR}"
+  OUTPUT_VARIABLE output
+)
+if (NOT MOC_RERUN)
+  message(SEND_ERROR "Initial build of automoc_rerun failed. Output: ${output}")
+endif()
+
+configure_file(automoc_rerun/test1.h.in2 automoc_rerun/test1.h COPYONLY)
+
+execute_process(COMMAND "${CMAKE_COMMAND}" --build .
+  WORKING_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/automoc_rerun"
+  RESULT_VARIABLE automoc_rerun_result
+  )
+if (automoc_rerun_result)
+  message(SEND_ERROR "Second build of automoc_rerun failed.")
+endif()

Tests/QtAutogen/automoc_rerun/CMakeLists.txt

@@ -0,0 +1,27 @@
+cmake_minimum_required(VERSION 3.1)
+project(automoc_rerun CXX)
+
+if (QT_TEST_VERSION STREQUAL 4)
+  find_package(Qt4 REQUIRED)
+  set(QT_CORE_TARGET Qt4::QtCore)
+else()
+  if (NOT QT_TEST_VERSION STREQUAL 5)
+    message(SEND_ERROR "Invalid Qt version specified.")
+  endif()
+
+  find_package(Qt5Core REQUIRED)
+  set(QT_CORE_TARGET Qt5::Core)
+endif()
+
+set(CMAKE_AUTOMOC ON)
+set(CMAKE_AUTORCC ON)
+
+configure_file(test1.h.in1 test1.h COPYONLY)
+
+add_executable(test1
+  ${CMAKE_CURRENT_BINARY_DIR}/test1.h
+  test1.cpp
+  res1.qrc
+  )
+target_include_directories(test1 PRIVATE ${CMAKE_CURRENT_BINARY_DIR})
+target_link_libraries(test1 ${QT_CORE_TARGET})

Tests/QtAutogen/automoc_rerun/input.txt

@@ -0,0 +1 @@
+Res1 input.

Tests/QtAutogen/automoc_rerun/res1.qrc

@@ -0,0 +1,5 @@
+<RCC>
+    <qresource prefix="/">
+        <file>input.txt</file>
+    </qresource>
+</RCC>

Tests/QtAutogen/automoc_rerun/test1.cpp

@@ -0,0 +1,5 @@
+#include "test1.h"
+int main()
+{
+  return 0;
+}

Tests/QtAutogen/automoc_rerun/test1.h.in1

@@ -0,0 +1,8 @@
+#include <QObject>
+class test1 : public QObject
+{
+  Q_OBJECT
+ public slots:
+   void onTst1() {}
+   void onTst2() {}
+};

Tests/QtAutogen/automoc_rerun/test1.h.in2

@@ -0,0 +1,7 @@
+#include <QObject>
+class test1 : public QObject
+{
+  Q_OBJECT
+ public slots:
+   void onTst1() {}
+};