Docker image builds hang on `apt-get update`

I'm seeing extremely slow container builds on Linux that hang at 100% CPU during `apt-get update`. I see very little network IO, disk IO, and memory consumption. I've let it run for >30 minutes to no avail.

Specifically, it looks like this is occurring for the `image-gcc`, `image-xcb`, and `image-build` targets.

I can't figure out how to get verbose output from `apt` here, any recommendations would be helpful I've been spinning my wheels on it for a while.

Is it possible I'm misinterpreting the output?

e.g.

```
❯ ./build-linux.py
...
image-gcc> Step 9/10 : RUN apt-get update
image-xcb> ---> Running in 64f6de138eb1
image-build> ---> Running in 3eb38e067d05
image-gcc> ---> Running in 2e0cd76e45bc
```

```
❯ docker stats
CONTAINER ID NAME CPU % MEM USAGE / LIMIT MEM % NET I/O BLOCK I/O PIDS
64f6de138eb1 gifted_khayyam 99.94% 1.145MiB / 31.25GiB 0.00% 18.6kB / 0B 0B / 0B 3
2e0cd76e45bc infallible_carver 100.15% 1.188MiB / 31.25GiB 0.00% 18.6kB / 0B 0B / 0B 3
3eb38e067d05 flamboyant_hellman 100.14% 1.121MiB / 31.25GiB 0.00% 18.6kB / 0B 0B / 0B 3
```

```
❯ docker inspect 2e0cd76e45bc
[
{
"Id": "2e0cd76e45bce897a34c096651987a0e373e06ede8e7922fac2cbe0d31d6af31",
"Created": "2024-03-20T17:52:31.490588566Z",
"Path": "/bin/sh",
"Args": [
"-c",
"apt-get update"
],
...
```

```
❯ docker exec -it 2e0cd76e45bc top

top - 17:57:24 up 1:55, 0 users, load average: 3.21, 3.33, 3.15
Tasks: 4 total, 2 running, 2 sleeping, 0 stopped, 0 zombie
%Cpu(s): 7.5 us, 12.3 sy, 0.0 ni, 80.0 id, 0.0 wa, 0.1 hi, 0.1 si, 0.0 st
KiB Mem: 32771652 total, 16323288 used, 16448364 free, 1327952 buffers
KiB Swap: 0 total, 0 used, 0 free. 6118300 cached Mem

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
8 root 20 0 29100 656 384 R 100.0 0.0 4:52.27 apt-get
1 root 20 0 4344 1280 1280 S 0.0 0.0 0:00.01 sh
7 root 20 0 29104 4352 4096 S 0.0 0.0 0:00.00 apt-get
15 root 20 0 21980 2432 2048 R 0.0 0.0 0:00.01 top

```

I can `docker build` a derived Dockerfile like

```Dockerfile
# Debian Jessie.
FROM debian@sha256:32ad5050caffb2c7e969dac873bce2c370015c2256ff984b70c1c08b3a2816a0
MAINTAINER Gregory Szorc

RUN groupadd -g 1000 build && \
useradd -u 1000 -g 1000 -d /build -s /bin/bash -m build && \
mkdir /tools && \
chown -R build:build /build /tools

ENV HOME=/build \
SHELL=/bin/bash \
USER=build \
LOGNAME=build \
HOSTNAME=builder \
DEBIAN_FRONTEND=noninteractive

CMD ["/bin/bash", "--login"]
WORKDIR '/build'

# Jessie's signing keys expired in late 2022. So need to add [trusted=yes] to force trust.
# Jessie stopped publishing snapshots in March 2023.
RUN for s in debian_jessie debian_jessie-updates debian-security_jessie/updates; do \
echo "deb [trusted=yes] http://snapshot.debian.org/archive/${s%_*}/20230322T152120Z/ ${s#*_} main"; \
done > /etc/apt/sources.list && \
( \
echo 'APT::Get::Assume-Yes "true";'; \
echo 'APT::Install-Recommends "false";'; \
echo 'Acquire::Check-Valid-Until "false";'; \
echo 'Acquire::Retries "5";'; \
) > /etc/apt/apt.conf.d/99cpython-portable

RUN ( echo 'amd64'; \
echo 'i386'; \
) > /var/lib/dpkg/arch

RUN apt-get update

RUN apt-get install \
autoconf \
automake \
bison \
build-essential \
gawk \
gcc \
gcc-multilib \
libtool \
make \
tar \
texinfo \
xz-utils \
unzip
```

with no issues.