WG14 N2350 made very clear that it is an UB having type definitions within "offsetof" [1]. This patch changes the implementation of macro check_alignof to builtin "_Alignof" to avoid undefined behavior.
clang 16+ has started to diagnose this [2]
Fixes build when using -std >= gnu11 and using clang16+
[1] https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2350.htm [2] https://reviews.llvm.org/D133574
Signed-off-by: Khem Raj raj.khem@gmail.com