git2 segfault reproducer

Trying to reproduce rust-lang/git2-rs#1057

NOTE: Cloning https://github.com/CVEProject/cvelistV5.git might take a while, but it seems to be required to trigger the issue.

What typically works

Run twice (or more) on aarch64-unknown-linux-gnu:

cargo run --release -- --path cvelistV5

What typically breaks

cross build --release --target aarch64-unknown-linux-gnu

Then (on an actual aarch64 target) run the following twice:

./git2-repro --path cvelistV5

Things to notice

I tried with a few other repos, but it seems to only fail with https://github.com/CVEProject/cvelistV5.git (the default).
- Also with https://github.com/NixOS/nixpkgs, but in this case with a different error:
```
free(): invalid size
fish: “./git2-repro --path test2 --sou…” terminated by signal SIGABRT (Abort)
```
Running on aarch64-unknown-linux-gnu works in general. But not when compiling with cross.
Using cross without --release also seems to work.

Faults

`https://github.com/CVEProject/cvelistV5.git`

[Current thread is 1 (Thread 0xffffb04e1f90 (LWP 268297))]
(gdb) where
#0  0x0000aaaab179252c in git_commit_list_insert_by_date ()
#1  0x0000aaaab1747d30 in git_revwalk.push_commit ()
#2  0x0000aaaab174828c in git_revwalk.push_glob ()
#3  0x0000aaaab176da10 in git_smart.negotiate_fetch ()
#4  0x0000aaaab1795c78 in git_fetch_negotiate ()
#5  0x0000aaaab173d4bc in git_remote.download ()
#6  0x0000aaaab173e75c in git_remote_fetch ()
#7  0x0000aaaab158ae04 in git2::remote::Remote::fetch ()
#8  0x0000aaaab1588dc0 in tracing::span::Span::in_scope ()
#9  0x0000aaaab15790b4 in git2_repro::run ()
#10 0x0000aaaab157f8cc in tokio::runtime::task::core::Core<T,S>::poll ()
#11 0x0000aaaab157fdbc in tokio::runtime::task::harness::Harness<T,S>::poll ()
#12 0x0000aaaab1641068 in std::sys_common::backtrace::__rust_begin_short_backtrace ()
#13 0x0000aaaab1649b18 in core::ops::function::FnOnce::call_once{{vtable-shim}} ()
#14 0x0000aaaab1a402b0 in <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once () at library/alloc/src/boxed.rs:2020
#15 <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once () at library/alloc/src/boxed.rs:2020
#16 std::sys::pal::unix::thread::Thread::new::thread_start () at library/std/src/sys/pal/unix/thread.rs:108
#17 0x0000ffffb0d33624 in start_thread (arg=0xaaaab1a40284 <std::sys::pal::unix::thread::Thread::new::thread_start>) at pthread_create.c:477
#18 0x0000ffffb0bcb62c in thread_start () at ../sysdeps/unix/sysv/linux/aarch64/clone.S:78
Warning: the current language does not match this frame.

`https://github.com/NixOS/nixpkgs`

[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/aarch64-linux-gnu/libthread_db.so.1".
Core was generated by `./git2-repro --path test2 --source https://github.com/NixOS/nixpkgs'.
Program terminated with signal SIGABRT, Aborted.
#0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
50      ../sysdeps/unix/sysv/linux/raise.c: No such file or directory.
[Current thread is 1 (Thread 0xffff9238af90 (LWP 267827))]
(gdb) where
#0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
#1  0x0000ffff929c3aac in __GI_abort () at abort.c:79
#2  0x0000ffff92a10f40 in __libc_message (action=action@entry=do_abort, fmt=fmt@entry=0xffff92ad26a8 "%s\n") at ../sysdeps/posix/libc_fatal.c:155
#3  0x0000ffff92a18344 in malloc_printerr (str=str@entry=0xffff92ace160 "free(): invalid size") at malloc.c:5347
#4  0x0000ffff92a19b98 in _int_free (av=0xffff92b11a98 <main_arena>, p=0xffff7ab9aff0, have_lock=<optimized out>) at malloc.c:4177
#5  0x0000aaaac99aef18 in git_signature_free ()
Backtrace stopped: previous frame identical to this frame (corrupt stack?)

Investigation

Ubuntu version
- It looks like cross' container images are based on Ubuntu 20.04: https://github.com/cross-rs/cross/blob/main/docker/Dockerfile.aarch64-unknown-linux-gnu.
- However, the apt sources in that image point to 16.04.
- In fact, the latest "released" version is Ubuntu 16.04: https://github.com/cross-rs/cross/blob/v0.2.5/docker/Dockerfile.aarch64-unknown-linux-gnu

Possible "fix"

Cross.toml:

[target.aarch64-unknown-linux-gnu]
image = "ghcr.io/cross-rs/aarch64-unknown-linux-gnu:edge"

ctron / git2-repro