First argument to ‘__builtin_choose_expr’ not a constant

[icmccorm]

When compiling libgit2 using cilly, I've encountered the following error:

/home/.../libgit2/src/libgit2/config_file.c:481:20: error: first argument to ‘__builtin_choose_expr’ not a constant
  481 |         config_file_backend *cfg = GIT_CONTAINER_OF(_cfg, config_file_backend, parent);
      |                    ^~~~~~~~~~~~~~~~~~~~~

This error does not occur when using only gcc. This is occurring on Ubuntu 22.04.1 LTS with gcc 11.2.