use CMake LTO module, enable LTO for MSVC build

.github/workflows/win_msvc.yml

@@ -53,7 +53,7 @@ jobs:
       - name: Configure
         run: |
           cmake -B build -G Ninja `
-            -DCMAKE_BUILD_TYPE=Release -DENABLE_WERROR=ON `
+            -DCMAKE_BUILD_TYPE=Release -DENABLE_WERROR=ON -DENABLE_LTO=ON`
             -DCMAKE_TOOLCHAIN_FILE="${{ env.VCPKG_ROOT }}/scripts/buildsystems/vcpkg.cmake" `
             -DVCPKG_TARGET_TRIPLET="${{ matrix.arch }}-windows-static-release" `
             -DVCPKG_OVERLAY_TRIPLETS="cmake/triplets"

CMakeLists.txt

@@ -12,7 +12,7 @@ list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake")
 set(CMAKE_POLICY_DEFAULT_CMP0077 NEW)
 set(X_VCPKG_APPLOCAL_DEPS_INSTALL ON)
 
-cmake_minimum_required(VERSION 3.6)
+cmake_minimum_required(VERSION 3.9)
 
 project("Woof"
     VERSION 10.5.1

cmake/WoofSettings.cmake

@@ -99,13 +99,11 @@ if(ENABLE_HARDENING)
     _checked_add_link_option(-Wl,-z,relro)
 endif()
 
-option(ENABLE_LTO "Enable link time optimization" OFF)
-if(ENABLE_LTO)
-    _checked_add_compile_option(-flto=auto)
-    _checked_add_compile_option(-ffat-lto-objects)
-    _checked_add_link_option(-flto=auto)
-    _checked_add_link_option(-ffat-lto-objects)
-endif()
+include(CheckIPOSupported)
+check_ipo_supported(RESULT HAVE_LTO)
+
+include(CMakeDependentOption)
+cmake_dependent_option(ENABLE_LTO "Enable link time optimization" OFF "HAVE_LTO" OFF)
 
 if(${FORCE_COLORED_OUTPUT})
     _checked_add_compile_option(-fdiagnostics-color=always F_DIAG_COLOR)
@@ -118,5 +116,6 @@ function(target_woof_settings)
     foreach(target ${ARGN})
         target_compile_options(${target} PRIVATE ${COMMON_COMPILE_OPTIONS})
         target_link_options(${target} PRIVATE ${COMMON_LINK_OPTIONS})
+        set_target_properties(${target} PROPERTIES INTERPROCEDURAL_OPTIMIZATION ${ENABLE_LTO})
     endforeach()
 endfunction()