openat2: #include <linux/types.h> so we can know __u64

Alternative implementations could use `uint64_t` instead, from `cstdint`.

Signed-off-by: Zygo Blaxell <bees@furryterror.org>

include/crucible/openat2.h

@@ -12,6 +12,8 @@
 
 #else
 
+#include <linux/types.h>
+
 #ifndef RESOLVE_NO_XDEV
 #define RESOLVE_NO_XDEV 1