CMake: Split target finalization code into a separate function

It was duplicated across a few public API.
Splitting it will also allow it to be be reused in a future change
in another function.

Also add the ability to use the poor man finalizer approach for
CMake 3.16, but only via an opt-in that will be set by the qt build
process, so that the finalizers can be used for tests in a future
change.

Task-number: QTBUG-93625
Task-number: QTBUG-112212
Change-Id: I097faf5e3db98457acfdfb3ae2011efb6640f35e
Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>
(cherry picked from commit 2bbc0bd)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

cmake/QtScopeFinalizerHelpers.cmake

@@ -88,6 +88,9 @@ function(qt_watch_current_list_dir variable access value current_list_file stack
                 elseif(func STREQUAL "_qt_internal_finalize_sbom")
                     _qt_internal_finalize_sbom(
                         ${a1} ${a2} ${a3} ${a4} ${a5} ${a6} ${a7} ${a8} ${a9})
+                elseif(func STREQUAL "qt6_finalize_target")
+                    qt6_finalize_target(
+                        ${a1} ${a2} ${a3} ${a4} ${a5} ${a6} ${a7} ${a8} ${a9})
                 else()
                     message(FATAL_ERROR "qt_watch_current_list_dir doesn't know about ${func}. Consider adding it.")
                 endif()

src/corelib/Qt6CoreMacros.cmake

@@ -652,17 +652,7 @@ function(qt6_add_executable target)
         return()
     endif()
 
-    # Defer the finalization if we can. When the caller's project requires
-    # CMake 3.19 or later, this makes the calls to this function concise while
-    # still allowing target property modification before finalization.
-    if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.19)
-        # Need to wrap in an EVAL CODE or else ${target} won't be evaluated
-        # due to special behavior of cmake_language() argument handling
-        cmake_language(EVAL CODE "cmake_language(DEFER CALL qt6_finalize_target ${target})")
-    else()
-        set_target_properties("${target}" PROPERTIES _qt_is_immediately_finalized TRUE)
-        qt6_finalize_target("${target}")
-    endif()
+    _qt_internal_finalize_target_defer("${target}")
 endfunction()
 
 # Just like for qt_add_resources, we should disable zstd compression when cross-compiling to a
@@ -861,6 +851,22 @@ function(qt6_finalize_target target)
     set_target_properties(${target} PROPERTIES _qt_is_finalized TRUE)
 endfunction()
 
+function(_qt_internal_finalize_target_defer target)
+    # Defer the finalization if we can. When the caller's project requires
+    # CMake 3.19 or later, this makes the calls to this function concise while
+    # still allowing target property modification before finalization.
+    if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.19)
+        # Need to wrap in an EVAL CODE or else ${target} won't be evaluated
+        # due to special behavior of cmake_language() argument handling
+        cmake_language(EVAL CODE "cmake_language(DEFER CALL qt6_finalize_target ${target})")
+    elseif(QT_BUILDING_QT AND QT_INTERNAL_USE_POOR_MANS_SCOPE_FINALIZER)
+        qt_add_list_file_finalizer(qt6_finalize_target "${target}")
+    else()
+        set_target_properties("${target}" PROPERTIES _qt_is_immediately_finalized TRUE)
+        qt6_finalize_target("${target}")
+    endif()
+endfunction()
+
 function(_qt_internal_finalize_source_groups target)
     if(NOT ("${CMAKE_GENERATOR}" STREQUAL "Xcode"
          OR "${CMAKE_GENERATOR}" MATCHES "^Visual Studio"))
@@ -2628,17 +2634,7 @@ function(qt6_add_plugin target)
         return()
     endif()
 
-    # Defer the finalization if we can. When the caller's project requires
-    # CMake 3.19 or later, this makes the calls to this function concise while
-    # still allowing target property modification before finalization.
-    if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.19)
-        # Need to wrap in an EVAL CODE or else ${target} won't be evaluated
-        # due to special behavior of cmake_language() argument handling
-        cmake_language(EVAL CODE "cmake_language(DEFER CALL qt6_finalize_target ${target})")
-    else()
-        set_target_properties("${target}" PROPERTIES _qt_is_immediately_finalized TRUE)
-        qt6_finalize_target("${target}")
-    endif()
+    _qt_internal_finalize_target_defer("${target}")
 endfunction()
 
 if(NOT QT_NO_CREATE_VERSIONLESS_FUNCTIONS)
@@ -2664,17 +2660,7 @@ function(qt6_add_library target)
         return()
     endif()
 
-    # Defer the finalization if we can. When the caller's project requires
-    # CMake 3.19 or later, this makes the calls to this function concise while
-    # still allowing target property modification before finalization.
-    if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.19)
-        # Need to wrap in an EVAL CODE or else ${target} won't be evaluated
-        # due to special behavior of cmake_language() argument handling
-        cmake_language(EVAL CODE "cmake_language(DEFER CALL qt6_finalize_target ${target})")
-    else()
-        set_target_properties("${target}" PROPERTIES _qt_is_immediately_finalized TRUE)
-        qt6_finalize_target("${target}")
-    endif()
+    _qt_internal_finalize_target_defer("${target}")
 endfunction()
 
 # Creates a library target by forwarding the arguments to add_library.