Only access non-locals after they're initialised

[aszlig]

This fixes a long-standing issue on aarch64, which is caused by mimalloc in Python 3 calling close too early:

#0  0x0000007ff75952ac in __pthread_kill_implementation () from .../lib/libc.so.6
#1  0x0000007ff753c5b8 in raise () from .../lib/libc.so.6
#2  0x0000007ff7525d38 in abort () from .../lib/libc.so.6
#3  0x0000007ff7299818 in __gnu_cxx::__verbose_terminate_handler() () from .../lib/libstdc++.so.6
#4  0x0000007ff729704c in __cxxabiv1::__terminate(void (*)()) () from .../lib/libstdc++.so.6
#5  0x0000007ff728e49c in std::terminate() () from .../lib/libstdc++.so.6
#6  0x0000007ff72973dc in __cxa_throw () from .../lib/libstdc++.so.6
#7  0x0000007ff728ed7c in std::__throw_bad_array_new_length() () from .../lib/libstdc++.so.6
#8  0x0000007ff7f10c54 in std::__new_allocator<std::__detail::_Hash_node_base*>::allocate (this=0x7fffffe890, __n=18446744073709551557) at .../include/c++/15.2.0/bits/new_allocator.h:139
#9  0x0000007ff7f6e898 in std::allocator_traits<std::allocator<std::__detail::_Hash_node_base*> >::allocate (__a=..., __n=18446744073709551557)
      at .../include/c++/15.2.0/bits/alloc_traits.h:614
#10 std::__detail::_Hashtable_alloc<std::allocator<std::__detail::_Hash_node<int, false> > >::_M_allocate_buckets (this=0x7ff7fb02a0 <all_fds>, __bkt_count=18446744073709551557)
      at .../include/c++/15.2.0/bits/hashtable_policy.h:1605
#11 0x0000007ff7f6e500 in std::_Hashtable<int, int, std::allocator<int>, std::__detail::_Identity, std::equal_to<int>, std::hash<int>, std::__detail::_Mod_range_hashing, std::__detail::_Default_ranged_hash, std::__detail::_Prime_rehash_policy, std::__detail::_Hashtable_traits<false, true, true> >::_M_allocate_buckets (this=0x7ff7fb02a0 <all_fds>, __bkt_count=18446744073709551557)
      at .../include/c++/15.2.0/bits/hashtable.h:413
#12 0x0000007ff7f6d944 in std::_Hashtable<int, int, std::allocator<int>, std::__detail::_Identity, std::equal_to<int>, std::hash<int>, std::__detail::_Mod_range_hashing, std::__detail::_Default_ranged_hash, std::__detail::_Prime_rehash_policy, std::__detail::_Hashtable_traits<false, true, true> >::_M_rehash (this=0x7ff7fb02a0 <all_fds>, __bkt_count=18446744073709551557) at .../include/c++/15.2.0/bits/hashtable.h:2754
#13 0x0000007ff7f6c0b8 in std::_Hashtable<int, int, std::allocator<int>, std::__detail::_Identity, std::equal_to<int>, std::hash<int>, std::__detail::_Mod_range_hashing, std::__detail::_Default_ranged_hash, std::__detail::_Prime_rehash_policy, std::__detail::_Hashtable_traits<false, true, true> >::_M_insert_unique_node (this=0x7ff7fb02a0 <all_fds>, __bkt=3, __code=3, __node=0x5555583580, __n_elt=1)
      at .../include/c++/15.2.0/bits/hashtable.h:2479
#14 0x0000007ff7f6a034 in std::_Hashtable<int, int, std::allocator<int>, std::__detail::_Identity, std::equal_to<int>, std::hash<int>, std::__detail::_Mod_range_hashing, std::__detail::_Default_ranged_hash, std::__detail::_Prime_rehash_policy, std::__detail::_Hashtable_traits<false, true, true> >::_M_emplace_uniq<int const&> (this=0x7ff7fb02a0 <all_fds>) at .../include/c++/15.2.0/bits/hashtable.h:2365
#15 0x0000007ff7f685a8 in std::_Hashtable<int, int, std::allocator<int>, std::__detail::_Identity, std::equal_to<int>, std::hash<int>, std::__detail::_Mod_range_hashing, std::__detail::_Default_ranged_hash, std::__detail::_Prime_rehash_policy, std::__detail::_Hashtable_traits<false, true, true> >::insert (this=0x7ff7fb02a0 <all_fds>, __v=@0x7fffffebb8: 3) at .../include/c++/15.2.0/bits/hashtable.h:1049
#16 0x0000007ff7f66b60 in std::unordered_set<int, std::hash<int>, std::equal_to<int>, std::allocator<int> >::insert (this=0x7ff7fb02a0 <all_fds>, __x=@0x7fffffebb8: 3)
      at .../include/c++/15.2.0/bits/unordered_set.h:475
#17 0x0000007ff7f64c80 in Systemd::init (rules=...) at ../src/systemd.cc:213
#18 0x0000007ff7f14bd0 in init_rules () at ../src/preload.cc:77
#19 0x0000007ff7f19edc in ip2unix_wrap_close (fd=4) at ../src/preload.cc:677
#20 0x0000007ff78cf430 in mi_process_init.part () from .../lib/libpython3.13.so.1.0
#21 0x0000007ff7894ee8 in _mi_process_init () from .../lib/libpython3.13.so.1.0
#22 0x0000007ff7fc32c4 in call_init () from .../lib/ld-linux-aarch64.so.1
#23 0x0000007ff7fc341c in _dl_init () from .../lib/ld-linux-aarch64.so.1
#24 0x0000007ff7fdbea0 in _start () from .../lib/ld-linux-aarch64.so.1

Here the non-local all_fds variable is an unordered_set which hasn't yet been initialised but is accessed because _mi_process_init has a lower priority and thus is initialised before all_fds.

Since mi_process_init calls close, an insert on the all_fds variable is triggered by the systemd rule initialisation, which then fails because all_fds hasn't been initialised yet.

The all_fds variable isn't the only one that's affected, so in order to avoid wrapping all non-local variables in lazy initalisation wrappers, we now short-circuit all the library calls that trigger the ruleset initialisation machinery.