[PATCH vkd3d] tests: Include <stddef.h> from "d3d12_crosstest.h". (Clang)

[Chip Davis]

Neither MinGW's nor Microsoft's <windows.h> includes <stddef.h>, either
directly or indirectly. Also, unlike GCC, Clang's <inttypes.h> does not
include <stddef.h>, either. "vkd3d_windows.h" does include <stddef.h>,
and this is why building for the host works, even with Clang.

Fixes cross compilation errors with Clang related to using offsetof(3).

Signed-off-by: Chip Davis 
---
 tests/d3d12_crosstest.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tests/d3d12_crosstest.h b/tests/d3d12_crosstest.h
index 43af375..0b77bde 100644
--- a/tests/d3d12_crosstest.h
+++ b/tests/d3d12_crosstest.h
@@ -52,6 +52,7 @@ typedef int HRESULT;
 #include <inttypes.h>
 #include <limits.h>
 #include <math.h>
+#include <stddef.h>
 #include <time.h>

#ifdef _WIN32