Fix disabling optimizations on Debug builds

Use /Od on MSVC and use our helper macro to detect support for the
flags, this avoid warnings on MSVC since it doesn't understand -O0.

Author: saghul

CMakeLists.txt

@@ -88,7 +88,8 @@ if(CMAKE_SYSTEM_NAME STREQUAL "WASI")
 endif()
 
 if(CMAKE_BUILD_TYPE MATCHES "Debug")
-    add_compile_options(-O0)
+    xcheck_add_c_compiler_flag(/Od)
+    xcheck_add_c_compiler_flag(-O0)
     xcheck_add_c_compiler_flag(-ggdb)
     xcheck_add_c_compiler_flag(-fno-omit-frame-pointer)
 endif()