CMAKE_BUILD_TYPE Checks Fail on Windows MSVC Builds

Running into trouble getting CMAKE_BUILD_TYPE checks to behave on Windows builds using MSVC. The project spans over 250 sub-projects, and a shared flags.cmake file included everywhere has been used to maintain consistency across configurations.

Why is CMAKE_BUILD_TYPE ignored on Windows?

The logic appears simple: verify the compiler ID, verify the build type, then append the flags. Here is the snippet causing trouble:

if (CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
 if(CMAKE_BUILD_TYPE STREQUAL "Debug")
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++2a -fcoroutines -fvisibility=hidden -fconcepts-diagnostics-depth=3 -Wno-attributes -Wall -Wextra -Wpedantic")
 else()
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++2a -fcoroutines -fvisibility=hidden")
 endif()
endif()
if (CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")
 set(CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS OFF)
 set(CMAKE_CXX_VISIBILITY_PRESET hidden)
 if(CMAKE_BUILD_TYPE STREQUAL "Debug")
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /EHsc /GR /utf-8 /fsanitize=address")
 else()
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /EHsc /GR /utf-8")
 endif()
endif()

set(global_defines -Dqor_pp_unicode)

The issue is that if(CMAKE_BUILD_TYPE STREQUAL "Debug") gets ignored on Windows. The flag /fsanitize=address leaks into non-Debug builds, wrecking performance and stability. This appears to be a known friction point among CMake, Ninja, and Visual Studio, with no urgent fix in sight.

Are Generator Expressions the right solution?

I've attempted to use LLMs to migrate to Generator Expressions, which should handle multi-config generators correctly, but the AI hallucinates the syntax. Every example it produces is slightly wrong or fails to compile. The official CMake documentation on Generator Expressions is extensive, yet finding a concrete, real-world example for toggling compiler flags by configuration is surprisingly difficult.

I've also heard about CMakePresets.json, but that feels like a massive migration. If I adopt presets, must I touch all 250+ sub-projects, or can I manage this globally?

How to enforce flags across build configurations?

I need a reliable AI-assisted workflow for my build system that strictly enforces flags for Debug, RelWithDebugInfo, and Release across GCC, Clang, and MSVC without manually editing hundreds of files. I'm after the correct modern CMake approach.

If you're considering suggesting a total switch to something like SCons or Jam, I'm specifically seeking a CMake-based solution right now to avoid a full infrastructure rewrite.