feat: Android build generation (#133)

[apotema]

Summary

• Add AndroidConfig struct (package_name, min/target SDK, orientation)
• Add Android template sections to build_zig.txt: NDK sysroot detection, shared library output, GLES3/EGL/libandroid linking
• Add Android branches to build_files.zig mirroring the iOS pattern

Key difference from iOS: output is a .so (shared library) for NativeActivity, not an executable.

Closes labelle-toolkit/labelle-cli#133

Test plan

• zig build compiles
• All existing tests pass
• Generate Android build.zig and verify cross-compilation (needs CLI commands from chore(sokol): un-pin from labelle-toolkit/sokol-zig fork; use upstream #134)

🤖 Generated with Claude Code

[cursor]

PR Summary

Medium Risk
Adds a new Android build generation path (shared-library output, NDK detection, and manual system lib linking), which may impact cross-compilation and platform-specific linking behavior.

Overview
Adds Android platform support to generated build.zig, including a new AndroidConfig on ProjectConfig and re-export via root.zig.

The generator now emits Android-specific template sections that detect the NDK sysroot, select device vs emulator targets, build a game shared library, and link required NDK/system libraries (plus optional GUI bridge and target_sdk_version-dependent library paths).

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[gemini-code-assist]

Code Review

This pull request introduces Android support to the build system by adding an AndroidConfig structure and implementing the corresponding generation logic in build_files.zig. The update includes a comprehensive template for Android builds that handles NDK detection, target resolution for both physical devices and emulators, and linking for the Sokol backend and Android system libraries. Feedback focuses on making the build template more robust by removing hardcoded architecture paths and API levels, which currently prevent emulator builds and ignore user configuration. Additionally, the NDK version detection logic should be improved to ensure the highest version is selected, and several redundant memory allocations and duplicated helper functions within the template should be cleaned up.

[gemini-code-assist]

To support both physical devices and emulators, the architecture-specific NDK paths should be derived from the target. Hardcoding aarch64-linux-android in the include and library paths (lines 481 and 513) will break the build when emulator_mode is enabled.

    const ndk_arch = if (emulator_mode) "x86_64-linux-android" else "aarch64-linux-android";

[gemini-code-assist]

Use the architecture-specific string derived from the target instead of hardcoding aarch64-linux-android.

    sokol_clib.root_module.addSystemIncludePath(.{ .cwd_relative = b.pathJoin(&.{ ndk_sysroot, "usr/include", ndk_arch }) });

[gemini-code-assist]

The AndroidConfig values (like target_sdk_version) are currently ignored during generation. The API level is hardcoded to 34 in the template. Consider using renderSection to pass the configured API level to the template.

        const android_cfg = cfg.android orelse config.AndroidConfig{};
        try tpl.renderSection(build_zig_tmpl, "android_link", .{ .target_sdk = android_cfg.target_sdk_version }, w);

[gemini-code-assist]

The library path should use the target architecture and the configured API level instead of hardcoded values.

    lib.root_module.addLibraryPath(.{ .cwd_relative = b.pathJoin(&.{ ndk_sysroot, "usr/lib", ndk_arch, "{{target_sdk}}" }) });

[gemini-code-assist]

The call to b.allocator.dupe is redundant here. b.pathJoin already allocates the resulting string using b.allocator. Since b.allocator in a Zig build script is typically an arena allocator, you can return the slice directly.

            return sysroot;

[gemini-code-assist]

The logic for finding the 'latest' NDK version is fragile because dir.iterate() does not guarantee any specific order. It will simply return the last directory encountered during iteration, which might not be the highest version. Consider using a basic string comparison or std.SemanticVersion to ensure the highest version number is selected.

[gemini-code-assist]

Redundant dupe call. b.pathJoin already allocates on b.allocator.

                return sysroot;

[gemini-code-assist]

This overrideImport helper is duplicated multiple times within the template file (e.g., lines 199, 373, and 551). Adding another copy increases maintenance overhead. Consider moving this helper to a shared .helpers section or ensuring it's only included once in the final output.

[cursor]

Cursor Bugbot has reviewed your changes and found 2 potential issues.

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