envbuilder causes OOM when pushing large image layers to cache

I have a `.devcontainer` with a `Dockerfile`:

```
FROM mcr.microsoft.com/vscode/devcontainers/base:ubuntu
# Install Ollama
RUN curl -fsSL https://ollama.com/install.sh | TERM=xterm sh
```

Ollama is about 3GB.

If I run envbuilder with ENVBUILDER_CACHE_REPO set, then the envbuilder process will cause an OOM (without CACHE_REPO, it completes):

```
docker run -it --rm \
-v $PWD:/workspace \
-e ENVBUILDER_WORKSPACE_FOLDER=/workspace \
-e ENVBUILDER_INIT_SCRIPT=bash \
-e ENVBUILDER_VERBOSE=1 \
-e ENVBUILDER_CACHE_REPO=".dkr.ecr.us-west-2.amazonaws.com/envbuilder-cache" \
ghcr.io/coder/envbuilder
envbuilder v1.1.0+a3a6a83 - Build development environments from repositories in a container
No Dockerfile specified, looking for a devcontainer.json...
Building in Devcontainer mode using /.devcontainer/devcontainer.json
<...>
#1: RUN curl -fsSL https://ollama.com/install.sh | TERM=xterm sh
#1: Using new RunMarker command
#1: Cmd: /bin/sh
#1: Args: [-c curl -fsSL https://ollama.com/install.sh | TERM=xterm sh]
#1: Util.Lookup returned: &{Uid:0 Gid:0 Username:root Name:root HomeDir:/root}
#1: Performing slow lookup of group ids for root
#1: Running: [/bin/sh -c curl -fsSL https://ollama.com/install.sh | TERM=xterm sh]
>>> Installing ollama to /usr/local
>>> Downloading Linux arm64 bundle
######################################################################## 100.0%
<...>
>>> Install complete. Run "ollama" from the command line.
#1: Files changed [/etc <...> /var/log/lastlog]
#1: Taking snapshot of files...
#1: Adding to layer: [/ /etc <...> /var/log/lastlog]
#1: Hash components for file: /, mode: drwxr-xr-x, mtime: 2025-04-25 21:54:31.26944614 +0000 UTC, size: 1000, user-id: 0, group-id: 0
<...>
#1: Hash components for file: /var/log/lastlog, mode: -rw-rw-r--, mtime: 2025-04-25 21:55:28.376418937 +0000 UTC, size: 48568, user-id: 0, group-id: 17
#1: Deleting in layer: map[]
#1: Build: composite key for command RUN curl -fsSL https://ollama.com/install.sh | TERM=xterm sh &{[sha256:67d45b84f79ba63114ea97192913a59fff14c262ed2b83d15c357ac1b910b453 |1 PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin RUN curl -fsSL https://ollama.com/install.sh | TERM=xterm sh]}
#1: Build: cache key for command RUN curl -fsSL https://ollama.com/install.sh | TERM=xterm sh f4c8cf5ad4c513d32c23f27b704b5f4dcea782b9d5b3b7c96ce96867e8de03d3
```
The docker container exits after this. Checking dmesg shows that envbuilder was selected for oom-kill.

That last line ("Build: cache key for command") comes from [kaniko](https://github.com/coder/kaniko/blob/main/pkg/executor/build.go#L441), indicating something after that point is causing the excess memory use.

Possibly related issue on Kaniko github: https://github.com/GoogleContainerTools/kaniko/issues/909

Tái hiện lỗi bằng lệnh docker run được cung cấp, một layer Ollama và ENVBUILDER_CACHE_REPO được thiết lập. Bắt đầu tại kaniko's pkg/executor/build.go#L441, nơi xuất hiện log cache-key, và lần theo đường dẫn push cache. Hoàn thành khi layer lớn có thể được cache mà không khiến envbuilder bị kết thúc do OOM.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.