[Bug c/53548] allow flexible array members in unions like zero-length arrays

[qinzhao at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53548

--- Comment #10 from qinzhao at gcc dot gnu.org ---
Clang has accept this extension:
https://github.com/llvm/llvm-project/pull/84428