fix: fix Hardening options and LTO for multi-configuration generators

[FeignClaims]

fix #259 by using generator expressions and CMAKE_INTERPROCEDURAL_OPTIMIZATION_<CONFIG>.

[FeignClaims]

From my personal test on MacOS M1 (unfortunately not implementable in Github Actions yet), check_ipo_supported() falsely failed because it can't find clang-scan-deps for "" -format=p1689.

The problem is that CMake 3.23 and below run the check with the current environment and toolchain settings. Since we specify cmake_minimum_required(VERSION 3.20) in Index.cmake, it performs as if cmake is v3.20, but CMake supports C++ Modules only after 3.28.

Here're two possible solutions:

• (chosen) In Index.cmake, use cmake_minimum_required(VERSION 3.24) instead of cmake_minimum_required(VERSION 3.20), which makes check_ipo_supported() prefer to honor the calling project's flags.
• Instead of calling enable_interprocedural_optimization() inside Index.cmake, force users to call enable_interprocedural_optimization(<prefix>_project_options) themselves in their project.

error log

CMake Warning at build/clang/_deps/_sample_project_project_options-src/src/Optimization.cmake:20 (message):
  Interprocedural Optimization is not supported.  Not using it.  Here is the
  error log: Change Dir:
  '/Users/feignclaims/code/cpp/cpp_conan_template/build/clang/CMakeFiles/_CMakeLTOTest-CXX/bin'




  Run Build Command(s): /opt/homebrew/bin/ninja -v

  [1/8] "" -format=p1689 -- /opt/homebrew/opt/llvm/bin/clang++
  -DCMAKE_INTDIR=\"Debug\" -stdlib=libc++ -L/opt/homebrew/opt/llvm/lib/c++
  -Wno-unused-command-line-argument -g -std=c++26 -flto=thin -arch arm64
  -isysroot
  /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.5.sdk
  -fPIC -x c++
  /Users/feignclaims/code/cpp/cpp_conan_template/build/clang/CMakeFiles/_CMakeLTOTest-CXX/src/foo.cpp
  -c -o CMakeFiles/foo.dir/Debug/foo.cpp.o -resource-dir
  "/opt/homebrew/Cellar/llvm/18.1.5/lib/clang/18" -MT
  CMakeFiles/foo.dir/Debug/foo.cpp.o.ddi -MD -MF
  CMakeFiles/foo.dir/Debug/foo.cpp.o.ddi.d >
  CMakeFiles/foo.dir/Debug/foo.cpp.o.ddi.tmp && mv
  CMakeFiles/foo.dir/Debug/foo.cpp.o.ddi.tmp
  CMakeFiles/foo.dir/Debug/foo.cpp.o.ddi

  FAILED: CMakeFiles/foo.dir/Debug/foo.cpp.o.ddi

  "" -format=p1689 -- /opt/homebrew/opt/llvm/bin/clang++
  -DCMAKE_INTDIR=\"Debug\" -stdlib=libc++ -L/opt/homebrew/opt/llvm/lib/c++
  -Wno-unused-command-line-argument -g -std=c++26 -flto=thin -arch arm64
  -isysroot
  /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.5.sdk
  -fPIC -x c++
  /Users/feignclaims/code/cpp/cpp_conan_template/build/clang/CMakeFiles/_CMakeLTOTest-CXX/src/foo.cpp
  -c -o CMakeFiles/foo.dir/Debug/foo.cpp.o -resource-dir
  "/opt/homebrew/Cellar/llvm/18.1.5/lib/clang/18" -MT
  CMakeFiles/foo.dir/Debug/foo.cpp.o.ddi -MD -MF
  CMakeFiles/foo.dir/Debug/foo.cpp.o.ddi.d >
  CMakeFiles/foo.dir/Debug/foo.cpp.o.ddi.tmp && mv
  CMakeFiles/foo.dir/Debug/foo.cpp.o.ddi.tmp
  CMakeFiles/foo.dir/Debug/foo.cpp.o.ddi

  /bin/sh: : command not found

  [2/8] "" -format=p1689 -- /opt/homebrew/opt/llvm/bin/clang++
  -DCMAKE_INTDIR=\"Debug\" -stdlib=libc++ -L/opt/homebrew/opt/llvm/lib/c++
  -Wno-unused-command-line-argument -g -std=c++26 -flto=thin -arch arm64
  -isysroot
  /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.5.sdk
  -fPIE -x c++
  /Users/feignclaims/code/cpp/cpp_conan_template/build/clang/CMakeFiles/_CMakeLTOTest-CXX/src/main.cpp
  -c -o CMakeFiles/boo.dir/Debug/main.cpp.o -resource-dir
  "/opt/homebrew/Cellar/llvm/18.1.5/lib/clang/18" -MT
  CMakeFiles/boo.dir/Debug/main.cpp.o.ddi -MD -MF
  CMakeFiles/boo.dir/Debug/main.cpp.o.ddi.d >
  CMakeFiles/boo.dir/Debug/main.cpp.o.ddi.tmp && mv
  CMakeFiles/boo.dir/Debug/main.cpp.o.ddi.tmp
  CMakeFiles/boo.dir/Debug/main.cpp.o.ddi

  FAILED: CMakeFiles/boo.dir/Debug/main.cpp.o.ddi

  "" -format=p1689 -- /opt/homebrew/opt/llvm/bin/clang++
  -DCMAKE_INTDIR=\"Debug\" -stdlib=libc++ -L/opt/homebrew/opt/llvm/lib/c++
  -Wno-unused-command-line-argument -g -std=c++26 -flto=thin -arch arm64
  -isysroot
  /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.5.sdk
  -fPIE -x c++
  /Users/feignclaims/code/cpp/cpp_conan_template/build/clang/CMakeFiles/_CMakeLTOTest-CXX/src/main.cpp
  -c -o CMakeFiles/boo.dir/Debug/main.cpp.o -resource-dir
  "/opt/homebrew/Cellar/llvm/18.1.5/lib/clang/18" -MT
  CMakeFiles/boo.dir/Debug/main.cpp.o.ddi -MD -MF
  CMakeFiles/boo.dir/Debug/main.cpp.o.ddi.d >
  CMakeFiles/boo.dir/Debug/main.cpp.o.ddi.tmp && mv
  CMakeFiles/boo.dir/Debug/main.cpp.o.ddi.tmp
  CMakeFiles/boo.dir/Debug/main.cpp.o.ddi

  /bin/sh: : command not found

  ninja: build stopped: subcommand failed.



Call Stack (most recent call first):
  build/clang/_deps/_sample_project_project_options-src/src/Index.cmake:212 (enable_interprocedural_optimization)
  build/clang/_deps/_sample_project_project_options-src/src/DynamicProjectOptions.cmake:257 (project_options)
  cmake/sample_project_custom_project_options.cmake:30 (dynamic_project_options)
  CMakeLists.txt:12 (include)

[FeignClaims]

All vcpkg-related cross tests failed after requiring CMake 3.24 as the minium version.

I compared the logs from the last test with this one. Maybe this is caused by github action caches... or something else

Help wanted. Fixed after setting the POLICY CMP0138 instead of bumping cmake to 3.24.

[ddassie-texa]

You can set a POLICY without the need to bump the minimum version:

if(POLICY CMP0138)
  cmake_policy(SET CMP0138 NEW)
endif()

[FeignClaims]

You can set a POLICY without the need to bump the minimum version:您可以设置 POLICY 而无需提高最低版本：

if(POLICY CMP0138)
  cmake_policy(SET CMP0138 NEW)
endif()

I forgot this solution, thanks.

[FeignClaims]

ci on Test (macos-13, gcc, true, true) fails, which refers to the known issue of github runners actions/runner-images#9997. Therefore, it's not related to this pr.

Given that the pull request performs well in other tests, I believe it is now suitable for review and possibly ready for merging.