Autogen: Restore target-ordering dependencies in Makefiles with DEPFILE

In commit aebfbcaa46 (AutoGen: Use depfiles for the XXX_autogen ninja
targets, 2020-01-14, v3.17.0-rc1~58^2) the `_autogen_timestamp_deps`
target was given target ordering dependencies through its custom command
rather than direct target dependencies as on the `_autogen` target.
Then commit 895fa3433f (cmQtAutoGenInitializer: support IMPLIB-only
imported targets, 2021-09-23, v3.22.0-rc1~80^2) converted some
target-level dependencies into file-level dependencies on the custom
command.  This only works with a monolithic build graph like Ninja.

Since commit ebc9e448b3 (Autogen: Add depfile support for Makefiles,
2023-09-07, v3.28.0-rc1~101^2~1) we use the `_autogen_timestamp_deps`
target in Makefile generators too.  This exposed the missing target
ordering dependency.

Fixes: #25766

Source/cmQtAutoGenInitializer.cxx

@@ -1386,27 +1386,19 @@ bool cmQtAutoGenInitializer::InitAutogenTarget()
       const auto timestampTargetName =
         cmStrCat(this->GenTarget->GetName(), "_autogen_timestamp_deps");
 
-      // Add additional autogen target dependencies to
-      // '_autogen_timestamp_deps'.
-      for (const cmTarget* t : this->AutogenTarget.DependTargets) {
-        std::string depname = t->GetName();
-        if (t->IsImported()) {
-          auto const ttype = t->GetType();
-          if (ttype == cmStateEnums::TargetType::STATIC_LIBRARY ||
-              ttype == cmStateEnums::TargetType::SHARED_LIBRARY ||
-              ttype == cmStateEnums::TargetType::UNKNOWN_LIBRARY) {
-            depname = cmStrCat("$<TARGET_LINKER_FILE:", t->GetName(), ">");
-          }
-        }
-        dependencies.emplace_back(std::move(depname));
-      }
-
       auto cc = cm::make_unique<cmCustomCommand>();
       cc->SetWorkingDirectory(this->Dir.Work.c_str());
       cc->SetDepends(dependencies);
       cc->SetEscapeOldStyle(false);
       cmTarget* timestampTarget = this->LocalGen->AddUtilityCommand(
         timestampTargetName, true, std::move(cc));
+
+      // Add additional autogen target dependencies to
+      // '_autogen_timestamp_deps'.
+      for (const cmTarget* t : this->AutogenTarget.DependTargets) {
+        timestampTarget->AddUtility(t->GetName(), false, this->Makefile);
+      }
+
       auto const isMake =
         this->GlobalGen->GetName().find("Make") != std::string::npos;
       if (this->AutogenTarget.DependOrigin && isMake) {

Tests/QtAutogen/AutogenTimestampDeps/CMakeLists.txt

@@ -8,4 +8,17 @@ add_custom_target(ProjectInfo
   COMMAND ${CMAKE_COMMAND} -P ${CMAKE_CURRENT_SOURCE_DIR}/cmake/UpdateProjectInfo.cmake
   BYPRODUCTS ${CMAKE_BINARY_DIR}/ProjectInfo.hpp)
 
+set(ext_lib ${CMAKE_CURRENT_BINARY_DIR}/ext-build/${CMAKE_STATIC_LIBRARY_PREFIX}ext${CMAKE_STATIC_LIBRARY_SUFFIX})
+include(ExternalProject)
+ExternalProject_Add(ext_target
+  SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/ext"
+  BINARY_DIR "${CMAKE_CURRENT_BINARY_DIR}/ext-build"
+  DOWNLOAD_COMMAND ""
+  INSTALL_COMMAND ""
+  BUILD_BYPRODUCTS "${ext_lib}"
+  )
+add_library(ext STATIC IMPORTED)
+set_property(TARGET ext PROPERTY IMPORTED_LOCATION "${ext_lib}")
+add_dependencies(ext ext_target)
+
 add_subdirectory(src)

Tests/QtAutogen/AutogenTimestampDeps/ext/CMakeLists.txt

@@ -0,0 +1,4 @@
+cmake_minimum_required(VERSION 3.28)
+project(Ext C)
+add_library(ext STATIC ext.c)
+set_property(TARGET ext PROPERTY ARCHIVE_OUTPUT_DIRECTORY "$<1:${CMAKE_CURRENT_BINARY_DIR}>")

Tests/QtAutogen/AutogenTimestampDeps/ext/ext.c

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

Tests/QtAutogen/AutogenTimestampDeps/src/CMakeLists.txt

@@ -2,3 +2,4 @@ add_executable(Exe main.cpp ${CMAKE_BINARY_DIR}/ProjectInfo.hpp)
 add_dependencies(Exe ProjectInfo)
 target_include_directories(Exe PRIVATE ${CMAKE_BINARY_DIR})
 target_link_libraries(Exe PRIVATE ${QT_QTCORE_TARGET})
+target_link_libraries(Exe PRIVATE ext)

Tests/QtAutogen/AutogenTimestampDeps/src/main.cpp

@@ -1,5 +1,6 @@
 #include "ProjectInfo.hpp"
+extern "C" int ext();
 int main(int argc, char* argv[])
 {
-  return 0;
+  return ext();
 }

Tests/QtAutogen/Tests.cmake

@@ -2,7 +2,11 @@
 ADD_AUTOGEN_TEST(AutogenOriginDependsOff autogenOriginDependsOff)
 ADD_AUTOGEN_TEST(AutogenOriginDependsOn)
 ADD_AUTOGEN_TEST(AutogenTargetDepends)
+
+set(Autogen_CTEST_OPTIONS --build-target Exe)
 ADD_AUTOGEN_TEST(AutogenTimestampDeps)
+unset(Autogen_CTEST_OPTIONS)
+
 ADD_AUTOGEN_TEST(AutoMocGeneratedFile)
 ADD_AUTOGEN_TEST(Complex QtAutogen)
 ADD_AUTOGEN_TEST(GlobalAutogenSystemUseInclude)