[Bug]: Cannot build containerization from scratch on a machine that is behind a network proxy

### I have done the following

- [x] I have searched the existing issues
- [x] If possible, I've reproduced the issue using the 'main' branch of this project

### Steps to reproduce

```
brew install container
container system start --enable-kernel-install

source ~/.swiftly/env.sh

git clone --depth 1 https://github.com/apple/containerization
cd containerization

swiftly install --use
./scripts/install-hawkeye.sh
make protos
make clean containerization docs
make -C vminitd linux-sdk
make fetch-default-kernel init
```

### Current behavior

Containerization fails to build the linux image

### Expected behavior

Not an error?

### Environment

```markdown
- OS: 26.5.2
- Xcode: 26.6
- Swift: swiftlang-6.3.3.1.3 clang-2100.1.1.101
```

### Relevant log output

```shell
#6 ERROR: process "/bin/sh -c apt-get update && apt-get install -y --no-install-recommends make e2fsprogs libarchive-dev libbz2-dev liblzma-dev libssl-dev && apt-get clean && rm -rf /var/lib/apt/lists/*" did not complete successfully: exit code: 100
------
> [linux/arm64 1/12] RUN apt-get update && apt-get install -y --no-install-recommends make e2fsprogs libarchive-dev libbz2-dev liblzma-dev libssl-dev && apt-get clean && rm -rf /var/lib/apt/lists/*:
37.75
37.75 Package make is not available, but is referred to by another package.
37.75 This may mean that the package is missing, has been obsoleted, or
37.75 is only available from another source
37.75
37.75 E: Package 'make' has no installation candidate
37.75 E: Unable to locate package libarchive-dev
37.75 E: Unable to locate package libbz2-dev
37.75 E: Unable to locate package liblzma-dev
37.75 E: Package 'libssl-dev' has no installation candidate
------
Error: unknown: "failed to solve: process "/bin/sh -c apt-get update && apt-get install -y --no-install-recommends make e2fsprogs libarchive-dev libbz2-dev liblzma-dev libssl-dev && apt-get clean && rm -rf /var/lib/apt/lists/*" did not complete successfully: exit code: 100"
make[1]: *** [linux-image] Error 1
make: *** [init] Error 2
```

### Code of Conduct

- [x] I agree to follow this project's Code of Conduct

Start by reproducing the failure with the listed commands and inspect the linux-image step invoked by `make init`, using the logged `apt-get update` and package-install command as the boundary. Trace how proxy settings reach that build; done means the listed packages resolve and `make fetch-default-kernel init` completes behind a proxy.

Written by the indexing model from the issue text.