fix: Android build template — libc.txt, addLibrary, Apple Silicon emulator

[apotema]

Summary

• Replace addSharedLibrary with addLibrary(.linkage = .dynamic) — addSharedLibrary was removed in Zig 0.15.2
• Generate android-libc.txt pointing at the NDK sysroot so Zig can resolve Android libc headers (Zig doesn't bundle Android libc unlike gnu/musl)
• --emulator flag now auto-detects host arch: Apple Silicon → arm64-v8a, Intel Mac → x86_64

Test plan

• labelle android build compiles without addSharedLibrary error
• Android game binary links correctly with NDK libc
• --emulator generates correct ABI target on both Apple Silicon and Intel Macs

[cursor]

PR Summary

Medium Risk
Touches Android build/link configuration and target selection, which can break cross-compilation and emulator/device packaging if the NDK paths or ABI detection are wrong.

Overview
Fixes Android build generation by switching from the removed addSharedLibrary API to addLibrary(.linkage = .dynamic).

Improves --emulator builds by auto-selecting x86_64 vs aarch64 based on the host (Intel vs Apple Silicon) and adjusting the NDK triple accordingly.

Adds generation of an android-libc.txt and wires it via setLibCFile so Zig can find Android libc headers/CRT in the NDK sysroot during compilation/linking.

^{Reviewed by Cursor Bugbot for commit ca5cba1. Bugbot is set up for automated code reviews on this repo. Configure here.}

[gemini-code-assist]

Code Review

This pull request significantly improves the Zig build script for Android development by adding dynamic support for emulators on different host architectures (Intel Mac vs. Apple Silicon). It now automatically resolves the correct emulator architecture (x86_64 or aarch64) and adjusts NDK pathing accordingly. The changes also include setting the library linkage to dynamic and introducing a mechanism to configure Zig's libc paths to the Android NDK sysroot, which is essential for resolving standard C headers. A review comment suggests using b.fmt instead of std.mem.concat for constructing the libc.txt content, which would improve readability and align with more idiomatic Zig build script practices.

[gemini-code-assist]

Using b.fmt is more idiomatic and readable for constructing multi-line strings in Zig build scripts compared to std.mem.concat. It also simplifies the code by removing the need for explicit error handling with catch @panic("OOM"), as b.fmt uses the build allocator which panics on failure by default.

    const libc_content = b.fmt(
        \\include_dir={s}
        \\sys_include_dir={s}
        \\crt_dir={s}
        \\msvc_lib_dir=
        \\kernel32_lib_dir=
        \\gcc_dir=
        \\
    , .{
        b.pathJoin(&.{ ndk_sysroot, "usr/include" }),
        b.pathJoin(&.{ ndk_sysroot, "usr/include", ndk_arch_triple }),
        b.pathJoin(&.{ ndk_sysroot, "usr/lib", ndk_arch_triple, "{{target_sdk_version}}" }),
    });

[Copilot]

Pull request overview

Updates the generated Android build.zig template to stay compatible with newer Zig build APIs and to improve Android cross-compilation ergonomics (NDK libc headers + emulator ABI selection).

Changes:

• Replace addSharedLibrary with addLibrary(.linkage = .dynamic) for Zig 0.15.2 compatibility.
• Generate and set an android-libc.txt so Zig can locate Android libc headers/crt files via the NDK sysroot.
• Make --emulator pick ABI based on the host architecture (Apple Silicon → arm64-v8a, Intel → x86_64).

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[Copilot]

The new Apple Silicon emulator support relies on finding the NDK sysroot, but getAndroidNdkSysroot() uses ndkHostTag() which currently always returns "darwin-x86_64" for macOS. On Apple Silicon with a standard arm64 NDK install (.../prebuilt/darwin-arm64/...), this will fail to locate the sysroot, so --emulator won’t work even though emulator_arch selects .aarch64. Update ndkHostTag() to incorporate the host CPU arch (e.g., return darwin-arm64 when the build host arch is .aarch64, and keep darwin-x86_64 for Intel).

[Copilot]

This change adds non-trivial Android-specific build logic (switching to addLibrary(.linkage = .dynamic) and generating/setting android-libc.txt for NDK sysroot headers), but the current test suite doesn’t appear to generate build.zig for .platform = .android and assert these key strings/sections. Adding a generator test that builds an Android config and checks for addLibrary + .linkage = .dynamic and setLibCFile("android-libc.txt", ...) would help prevent regressions across Zig/NDK updates.