Use static assert in Clay engine to ensure struct alignment

source/blender/blenlib/BLI_utildefines.h

@@ -674,6 +674,9 @@ extern bool BLI_memory_is_zero(const void *arr, const size_t arr_size);
 #  define BLI_STATIC_ASSERT(a, msg)
 #endif
 
+#define BLI_STATIC_ASSERT_ALIGN(st, align) \
+  BLI_STATIC_ASSERT((sizeof(st) % (align) == 0), "Structure must be strictly aligned")
+
 /* hints for branch prediction, only use in code that runs a _lot_ where */
 #ifdef __GNUC__
 #  define LIKELY(x)       __builtin_expect(!!(x), 1)

source/blender/draw/engines/clay/clay_engine.c

@@ -57,6 +57,7 @@ typedef struct CLAY_UBO_Material {
 	float matcap_rot[2];
 	float pad[2]; /* ensure 16 bytes alignement */
 } CLAY_UBO_Material; /* 48 bytes */
+BLI_STATIC_ASSERT_ALIGN(CLAY_UBO_Material, 16);
 
 #define MAX_CLAY_MAT 512 /* 512 = 9 bit material id */