Nix: Add OpenBIOS to the build and refactor derivation

[NotExactlySiev]

The Nix build now ships with OpenBIOS. Also cleaned up the recipe a bit.
Also bumped up the number of build threads to 4, so the Github action build time has stayed the same even tho we're building the cross compiler too lol

[coderabbitai]

Walkthrough

The changes update the Nix flake configuration and the pcsx-redux package build script. In flake.nix, package definitions now differentiate between legacy and cross-compilation imports (for the mipsel target) and explicitly set the default package as pcsx-redux. Additionally, GitHub Actions checks are revised to prevent double builds. In pcsx-redux.nix, individual GitHub submodule fetches are consolidated into a structured list with a new helper function fetchSubmodule, and build configurations have been refined with updated inputs, increased parallel cores, and conditional build flags.

Changes

File(s)	Change Summary
flake.nix	Modified package definitions to separate legacy and cross compilations (for mipsel-none-elf), added a default entry for pcsx-redux, and updated GitHub Actions checks to avoid double builds. Also updated the gccMips reference to use cross-compilation packages.
pcsx-redux.nix	Consolidated multiple GitHub submodule fetches into a single structured submodules list and introduced the fetchSubmodule function. Updated build inputs to include zip, conditionally add gccMips based on the withOpenbios flag, increased NIX_BUILD_CORES to 4, and adjusted make/install flags accordingly.

Sequence Diagram(s)

sequenceDiagram
    participant S as System
    participant FN as Flake.nix
    participant PKG as Package Manager
    S->>FN: Trigger build process
    FN->>PKG: Import legacy packages for ${system}
    FN->>PKG: Import cross packages (mipsel-none-elf)
    FN->>PKG: Set default package to pcsx-redux
    FN->>PKG: Update GitHub Actions to remove defaults

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sequenceDiagram
    participant B as Build Process
    participant PX as pcsx-redux.nix
    participant SM as GitHub Submodule
    B->>PX: Initiate source unpacking
    PX->>PX: Iterate over submodules via fetchSubmodule
    PX->>SM: Request submodule details (owner, repo, revision, hash)
    SM-->>PX: Return submodule outputs
    PX->>B: Copy outputs and update build inputs
    B->>PX: Continue build with new configurations

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Poem

I'm a bunny with a code-filled dream,
Hopping through flakes with a nimble scheme.
Cross-compiling carrots for a mipsel bite,
Submodules fetched, everything feels right.
In tunnels of build scripts, I happily play,
Celebrating clean changes in my quirky way! 🥕

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📥 Commits

Reviewing files that changed from the base of the PR and between 0e6eda7 and 92d5c65.

⛔ Files ignored due to path filters (1)

• flake.lock is excluded by !**/*.lock

📒 Files selected for processing (2)

• flake.nix (1 hunks)
• pcsx-redux.nix (3 hunks)

⏰ Context from checks skipped due to timeout of 90000ms (11)

• GitHub Check: pcsx-redux (aarch64-linux)
• GitHub Check: pcsx-redux (x86_64-linux)
• GitHub Check: Codacy Static Code Analysis
• GitHub Check: build
• GitHub Check: build-openbios
• GitHub Check: cross-arm64
• GitHub Check: asan
• GitHub Check: macos-build-and-test-toolchain
• GitHub Check: toolchain
• GitHub Check: coverage
• GitHub Check: aur-build

🔇 Additional comments (12)

flake.nix (4)

27-33: Well-structured cross-compilation setup

The changes introduce a clear separation between regular packages (pkgs) and cross-compilation environment (cross). This structure improves maintainability by explicitly defining the cross-compilation target as "mipsel-none-elf", which is appropriate for PlayStation 1 development.

---

34-35: Explicitly defining the default package

Setting pcsx-redux as the default package is a good practice. It makes the intended primary package clear and simplifies usage for consumers of the flake.

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39-39: Appropriate cross-compiler reference

Using cross.buildPackages.gccWithoutTargetLibc for the MIPS compiler is correct for this use case, as it provides the necessary toolchain without including target libraries that might conflict with OpenBIOS's custom environment.

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44-47: Preventing redundant builds in CI

This change prevents GitHub Actions from building the same package twice by removing the default attribute. This is an efficiency improvement that avoids wasting CI resources.

pcsx-redux.nix (8)

29-29: Added required dependencies for OpenBIOS

The addition of zip as a dependency and the new withOpenbios parameter are appropriate for supporting the OpenBIOS build process.

Also applies to: 35-35

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39-104: Excellent refactoring of submodule management

The consolidation of individual fetchFromGitHub calls into a structured submodules list significantly improves code organization and maintainability. The conditional inclusion of platform-specific and OpenBIOS-specific repositories using lib.optional is elegant and follows Nix best practices.

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106-108: Good utility function for DRY implementation

The fetchSubmodule function eliminates repetitive code by encapsulating the fetching and copying logic. This follows the DRY (Don't Repeat Yourself) principle and makes the code more maintainable.

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114-117: Streamlined post-unpack process

The updated postUnpack phase effectively uses the new fetchSubmodule function with concatStringsSep to process all submodules in a clean, functional manner.

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122-127: Well-structured conditional dependencies

The conditional inclusion of MIPS compiler tools and zip when withOpenbios is enabled is appropriate. Unwrapping the compiler components ensures they're directly accessible during the build process.

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153-157: Improved make flags with conditional OpenBIOS build

The updated makeFlags correctly includes the OpenBIOS target conditionally, along with necessary prefix settings for the MIPS cross-compiler.

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159-163: Properly separated install flags

Separating installFlags from makeFlags improves clarity and follows standard Nix practice. The conditional inclusion of "install-openbios" is consistent with the overall approach to making OpenBIOS support optional.

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170-170: Appropriate build parallelism increase

Increasing NIX_BUILD_CORES from 2 to 4 aligns with the PR objective to maintain build performance despite the added complexity of the cross-compiler and OpenBIOS.

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[Copilot]

Copilot reviewed 1 out of 3 changed files in this pull request and generated no comments.

Files not reviewed (2)

• flake.nix: Language not supported
• pcsx-redux.nix: Language not supported