skill-build-systemslisted

# Skill: Build Systems Fast, reproducible, hermetic builds. No network calls. Same output every time. ## Hermetic Builds **Requirements**: - ✓ All dependencies vendored (in repo or locked) - ✓ No network calls during build - ✓ Deterministic output (bit-for-bit same) - ✓ Works offline **Example** (Bazel): ``` bazel build //app:binary → uses //third_party/go/dependencies.bzl (locked) → no network needed → same binary every time ``` ## Reproducible Builds ```bash # Build 1 $ bazel build //app --action_env=BUILD_TIME=0 $ sha256sum bazel-bin/app/binary → abc123... # Build 2 (week later) $ bazel build //app --action_env=BUILD_TIME=0 $ sha256sum bazel-bin/app/binary → abc123... # Identical! ``` ## Caching Strategy - **Local cache**: ~/.cache/bazel (fast) - **Shared cache**: S3/GCS (team) - **CI cache**: Previous builds (speed up) **Cache hit = skip recompilation** ## Dependency Locking ```yaml # dependencies.lock requests: version: 2.28.0 sha256: abc123... url: https://pypi.org/packages/... urllib3: version: 1.26.0 sha256: def456... ``` **Freeze dependencies** → reproducible ## Build Optimization - **Parallelism**: `-j 8` (8 parallel builds) - **Incremental**: Only rebuild changed files - **Caching**: Reuse previous outputs - **Sandboxing**: Isolation (prevents hidden dependencies) ## Binary Optimization ```bash # Strip debug symbols $ strip -s app # Compress $ upx -9 app # Size reduction: 50MB → 5MB ``` --- **Status**: Ready for build work **Best