cmake: remove /RTC1 from CXX flags when building with SDL_LIBC=OFF

CMakeLists.txt

@@ -189,9 +189,12 @@ if(MSVC)
     # Make sure /RTC1 is disabled, otherwise it will use functions from the CRT
     foreach(flag_var
         CMAKE_C_FLAGS CMAKE_C_FLAGS_DEBUG CMAKE_C_FLAGS_RELEASE
-        CMAKE_C_FLAGS_MINSIZEREL CMAKE_C_FLAGS_RELWITHDEBINFO)
+        CMAKE_C_FLAGS_MINSIZEREL CMAKE_C_FLAGS_RELWITHDEBINFO
+        CMAKE_CXX_FLAGS CMAKE_CXX_FLAGS_DEBUG CMAKE_CXX_FLAGS_RELEASE
+        CMAKE_CXX_FLAGS_MINSIZEREL CMAKE_CXX_FLAGS_RELWITHDEBINFO)
       string(REGEX REPLACE "/RTC(su|[1su])" "" ${flag_var} "${${flag_var}}")
     endforeach(flag_var)
+    set(CMAKE_MSVC_RUNTIME_CHECKS "")
   endif()
 
   if(MSVC_CLANG)