VC+d3d12: spread test for __has_include and d3d12.h test over multiple lines

include/build_config/SDL_build_config_windows.h

@@ -92,9 +92,11 @@ typedef unsigned int uintptr_t;
 #define HAVE_D3D11_H 1
 #define HAVE_ROAPI_H 1
 #endif
-#if defined(__has_include) && __has_include(<d3d12.h>) && __has_include(<d3d12sdklayers.h>)
+#if defined(__has_include)
+#if __has_include(<d3d12.h>) && __has_include(<d3d12sdklayers.h>)
 #define HAVE_D3D12_H 1
 #endif
+#endif
 #if defined(_WIN32_MAXVER) && _WIN32_MAXVER >= 0x0603  /* Windows 8.1 SDK */
 #define HAVE_SHELLSCALINGAPI_H 1
 #endif