guix: Compile GUI separately from other binaries #35098

This PR isolates the GUI build, including its specific dependencies, into a dedicated container.

Benefits of this approach:

1. Improves security: Any unknown backdoors in GUI-specific dependencies will no longer affect bitcoind and other non-GUI binaries.

2. Enables a safer upgrade path: Allows for the introduction of additional GUI dependencies needed for Wayland support or transitioning to the QML-based GUI.

3. ~Could be useful for #25573.~

This implementation is based on an idea proposed here.

Currently based on #34948 and #35072.

Closes #29914.

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Reviews

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Conflicts

Reviewers, this pull request conflicts with the following ones:

• #35131 (guix, refactor: Minor script cleanups and improvements by hebasto)
• #35072 (cmake: Remove optional definitions from bitcoin-build-config.h by hebasto)
• #34948 (guix: Split manifest into build and codesign manifests by hebasto)
• #32764 (guix: Build for macOS using Clang only by hebasto)
• #32162 (depends: Switch from multilib to platform-specific toolchains by hebasto)
• #31260 (scripted-diff: Type-safe settings retrieval by ryanofsky)
• #25573 (guix: produce a -static-pie bitcoind by fanquake)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

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🚧 At least one of the CI tasks failed. _{Task lint: https://github.com/bitcoin/bitcoin/actions/runs/24561368833/job/71811492362} _{LLM reason (✨ experimental): CI failed because the shell lint check (lint-shell.py) reported a ShellCheck SC2206 word-splitting warning in contrib/guix/libexec/build.sh and treated it as an error.}

<details><summary>Hints</summary>

Try to run the tests locally, according to the documentation. However, a CI failure may still happen due to a number of reasons, for example:

• Possibly due to a silent merge conflict (the changes in this pull request being incompatible with the current code in the target branch). If so, make sure to rebase on the latest commit of the target branch.

• A sanitizer issue, which can only be found by compiling with the sanitizer and running the affected test.

• An intermittent issue.

Leave a comment here, if you need help tracking down a confusing failure.

</details>

My Guix build:

aarch64
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b8136a36ca039e4db008a7ba3694be1a3ef5b8497a28ff0430ca4cea16e2fdab  guix-build-c4730955ec14/output/riscv64-linux-gnu/SHA256SUMS.part
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or transitioning to the QML-based GUI.

Is that blocked on this change; I thought it just needed to be finished? (looking at https://github.com/bitcoin-core/gui-qml, it just has this repo as a subtree; I also can't see any new dependencies)

Could be useful for #25573.

Im not sure yet, given the current approach of re-using the same build dir. We will want to compile / link the static binaries with different compilation / link flags.

or transitioning to the QML-based GUI.

Is that blocked on this change; I thought it just needed to be finished? (looking at https://github.com/bitcoin-core/gui-qml, it just has this repo as a subtree; I also can't see any new dependencies)

The qt6 branch using this repo as a subtree is a shortcut taken during the migration from Qt 5 to Qt 6.

The transition to QML-based GUI will use a branch that is cleanly mergeable into the master branch in this repo (rebasing is currently in progress).

The new dependencies will look like the ones here.

Could be useful for #25573.

Im not sure yet, given the current approach of re-using the same build dir. We will want to compile / link the static binaries with different compilation / link flags.

Dropped this from the PR description. However, it still seems unreasonable to keep GUI-specific stuff in a Guix prefix where static non-GUI binaries are being built.

The new dependencies will look like the ones here.

Ok, so some additional Qt subcomponents? My point is that doing anything QML related in this repo, doesn't seem to be blocked on the changes here. It could be done today, by just enabling a few more components in Qt, without any other, new, non-Qt dependencies?

The new dependencies will look like the ones here.

Ok, so some additional Qt subcomponents? My point is that doing anything QML related in this repo, doesn't seem to be blocked on the changes here. It could be done today, by just enabling a few more components in Qt, without any other, new, non-Qt dependencies?

I'm a bit confused. Are we making a distinction between additional Qt components and other non-Qt dependencies? If so, what is the difference between them from a security perspective?

This PR is not proposed solely for the transition to the QML-based GUI. Its primary purpose is to resolve #29914, which doesn't mention QML at all. As a byproduct, it also enables the transition to the QML GUI without having any effect on the security of the non-GUI release binaries.

I'm a bit confused. Are we making a distinction between additional Qt components and other non-Qt dependencies? If so, what is the difference between them from a security perspective?

Yes. I think we could generally add new Qt submodules as-needed, given we are already using Qt. Any other new dependency should be evaluated on a case-by-case basis.

it also enables the transition to the QML GUI without having any effect on the security of the non-GUI release binaries.

I think this is my confusion. I don't think there are any security-related issues that would arise from moving to QML, today, if it only requires using a few more Qt modules; so am trying to clarify how this PR provides a "safer upgrade path".