Fix repro-build fetch and dstack-mr cargo

[kvinwang]

Summary

• bump meta-virtualization to include a docker-compose fetch fix
• fetch github.com/moby/buildkit Go modules via git in hybrid mode instead of proxy.golang.org
• install Rust 1.92 via rustup in the reproducible-build Docker image so post-bitbake mkimage.sh can build dstack-mr
• bump the dstack submodule to the SEV-SNP branch containing dstack-mr sev-os-image-hash

Testing

• git -C meta-virtualization diff --check
• validated hybrid module cache data parses as JSON and contains buildkit v0.26.2/v0.27.1
• git ls-remote https://github.com/moby/buildkit.git refs/tags/v0.26.2^{} refs/tags/v0.27.1^{}
• docker build --platform linux/amd64 -t dstack-build-rustup-test -f repro-build/Dockerfile.repro repro-build/.dummy
• docker run --rm --userns=host --user $(id -u):$(id -g) dstack-build-rustup-test bash -lc 'cargo --version; rustc --version'
• docker run --rm --userns=host --user $(id -u):$(id -g) -v /home/kvin/src/meta-dstack:/meta-dstack -w /meta-dstack/dstack dstack-build-rustup-test bash -lc 'cargo build --release -p dstack-mr --target-dir /tmp/dstack-mr-target && /tmp/dstack-mr-target/release/dstack-mr --help'

[Copilot]

Pull request overview

This PR updates the meta-virtualization layer revision to pick up a fix for docker-compose builds where fetching github.com/moby/buildkit Go modules via proxy.golang.org can lead to do_fetch timeouts/failures in repro-build contexts. The intended outcome is more reliable module fetching by switching those BuildKit module downloads to a git-based approach (hybrid mode).

Changes:

• Bump the meta-virtualization submodule to a newer commit containing the docker-compose BuildKit fetch fix.
• Adjust BuildKit Go module fetching behavior for docker-compose to use git/hybrid mode instead of proxy.golang.org.

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