ci: cache Android NDK to speed up builds

[AnthonyRonning]

Enable local-cache: true option in nttld/setup-ndk action to avoid re-downloading the ~1.5GB NDK on every CI run.

This affects:

• .github/workflows/android-build.yml (rust-build job matrix - 4 parallel jobs)
• .github/workflows/release.yml (android-rust-build job matrix - 4 parallel jobs)

The NDK will be cached per runner OS and shared across all matrix jobs.

Summary by CodeRabbit

• Chores
  • Optimized CI/CD workflow performance by enabling local caching for Android NDK in build pipelines.

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[coderabbitai]

📝 Walkthrough

Walkthrough

Added local-cache: true configuration to the Android NDK setup step in two GitHub Actions workflow files. This enables local caching for the NDK path, optimizing build performance by reusing cached NDK artifacts across workflow runs.

Changes

Cohort / File(s)	Summary
Android NDK Local Caching ​.github/workflows/android-build.yml, ​.github/workflows/release.yml	Added local-cache: true to the Setup Android NDK step in both files to enable local caching of NDK artifacts for improved build performance. Identical configuration change applied to both workflows.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Possibly related PRs

• fix(ci): update Java 17->21 and NDK r25c->r27c to match local environ… #332: Modifies the same "Setup Android NDK" step by updating ndk-version and Java configuration alongside caching enablement.
• ci: parallelize Android Rust builds across all 4 architectures #386: Updates Android NDK setup in the same workflow files as part of a larger Android CI refactoring effort.
• Add android to release workflow #257: Introduces the release workflow that includes a "Setup Android NDK" step affected by caching optimizations.

Poem

🐰 Hop-hop, the cache is alive!
Local NDK keeps workflows thriving,
No more downloads, just reuse with glee,
Faster builds for you and me! 🚀

🚥 Pre-merge checks | ✅ 2

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and specifically describes the main change: enabling Android NDK caching in CI workflows to improve build performance.

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[greptile-apps]

Greptile Overview

Greptile Summary

Enables local caching for Android NDK downloads in CI workflows by adding local-cache: true to the nttld/setup-ndk action.

• Affects 8 parallel jobs across CI and release workflows (4 in each)
• Caches ~1.5GB NDK package per runner OS
• Cache is shared across matrix jobs on the same runner
• No code logic changes, only workflow optimization

Confidence Score: 5/5

• This PR is safe to merge with minimal risk
• Single configuration change to enable caching of NDK downloads with no logic modifications, using a well-established GitHub Action parameter
• No files require special attention

Sequence Diagram

sequenceDiagram
    participant GHA as GitHub Actions
    participant Cache as GitHub Actions Cache
    participant NDK as nttld/setup-ndk Action
    participant Download as NDK Download Source
    
    GHA->>NDK: Execute setup-ndk with local-cache: true
    NDK->>Cache: Check for cached NDK r27c
    
    alt Cache Hit
        Cache-->>NDK: Return cached NDK (~1.5GB)
        NDK->>GHA: NDK ready (fast path)
    else Cache Miss
        NDK->>Download: Download NDK r27c
        Download-->>NDK: NDK package (~1.5GB)
        NDK->>Cache: Store NDK in cache
        NDK->>GHA: NDK ready (slow path)
    end
    
    Note over GHA,Cache: Cache shared across matrix jobs<br/>on same runner OS

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