In the build log, it complains about mismatching pointer types.

In the upstream git repository, an issue was opened about a build error which looks very similar, pointing to an incompatibility with later glibc versions: https://github.com/lxc/lxc/issues/4183

I don't have the time to write and test a patch for it at this moment, but the solution looks to be updating the lxc package to a later supported version.

Here is what I believe to be the relevant part of the log:
mount_utils.c: In function ‘create_detached_idmapped_mount’:
mount_utils.c:297:29: error: passing argument 4 of ‘mount_setattr’ from incompatible pointer type [-Werror=incompatible-pointer-types]
  297 |                             &attr, sizeof(attr));
      |                             ^~~~~
      |                             |
      |                             struct lxc_mount_attr *
In file included from mount_utils.c:9:
/gnu/store/zvlp3n8iwa1svxmwv4q22pv1pb1c9pjq-glibc-2.39/include/sys/mount.h:320:46: note: expected ‘struct mount_attr *’ but argument is of type ‘struct lxc_mount_attr *’
  320 |                           struct mount_attr *__uattr, size_t __usize)
      |                           ~~~~~~~~~~~~~~~~~~~^~~~~~~
mount_utils.c: In function ‘__fd_bind_mount’:
mount_utils.c:380:37: error: passing argument 4 of ‘mount_setattr’ from incompatible pointer type [-Werror=incompatible-pointer-types]
  380 |                                     &attr, sizeof(attr));
      |                                     ^~~~~
      |                                     |
      |                                     struct lxc_mount_attr *
In file included from mount_utils.c:9:
/gnu/store/zvlp3n8iwa1svxmwv4q22pv1pb1c9pjq-glibc-2.39/include/sys/mount.h:320:46: note: expected ‘struct mount_attr *’ but argument is of type ‘struct lxc_mount_attr *’
  320 |                           struct mount_attr *__uattr, size_t __usize)
      |                           ~~~~~~~~~~~~~~~~~~~^~~~~~~
conf.c: In function ‘__lxc_idmapped_mounts_child’:
conf.c:2989:37: error: passing argument 4 of ‘mount_setattr’ from incompatible pointer type [-Werror=incompatible-pointer-types]
2989 |                                     &attr,
      |                                     ^~~~~
      |                                     |
      |                                     struct lxc_mount_attr *
In file included from conf.c:22:
/gnu/store/zvlp3n8iwa1svxmwv4q22pv1pb1c9pjq-glibc-2.39/include/sys/mount.h:320:46: note: expected ‘struct mount_attr *’ but argument is of type ‘struct lxc_mount_attr *’
  320 |                           struct mount_attr *__uattr, size_t __usize)
      |                           ~~~~~~~~~~~~~~~~~~~^~~~~~~
conf.c:3012:41: error: passing argument 4 of ‘mount_setattr’ from incompatible pointer type [-Werror=incompatible-pointer-types]
3012 |                                         &attr,
      |                                         ^~~~~
      |                                         |
      |                                         struct lxc_mount_attr *
In file included from conf.c:22:
/gnu/store/zvlp3n8iwa1svxmwv4q22pv1pb1c9pjq-glibc-2.39/include/sys/mount.h:320:46: note: expected ‘struct mount_attr *’ but argument is of type ‘struct lxc_mount_attr *’
  320 |                           struct mount_attr *__uattr, size_t __usize)
      |                           ~~~~~~~~~~~~~~~~~~~^~~~~~~

Best regards,
Kasper