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

(cherry picked from commit cfb8e591cb99068a39f834900863610ba3780553)

CMakeLists.txt

@@ -188,9 +188,12 @@ 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)