SDL_fillrect.c: updated SSE_BEGIN macro for windows clang-cl

from a patchset by Vladislav Dmitrievich Turbanov:
https://github.com/libsdl-org/SDL/pull/4062

src/video/SDL_fillrect.c

@@ -28,7 +28,7 @@
 #ifdef __SSE__
 /* *INDENT-OFF* */
 
-#ifdef _MSC_VER
+#if defined(_MSC_VER) && !defined(__clang__)
 #define SSE_BEGIN \
     __m128 c128; \
     c128.m128_u32[0] = color; \