Rust Build Analysis and Optimization

Diagnose slow Rust builds by measuring first, then apply the smallest fix that targets the actual bottleneck. The useful outcome is: a baseline number, a named bottleneck backed by profiler output, applied configuration changes, and a re-measured result — not a pile of speculative config.

Path note: <skill-dir> below means this skill's own directory. Substitute the literal path announced when the skill loads; do not use $SKILL_DIR.

Hard Rules

• Never recommend a fix before at least one measurement supports it.
• Label every nightly-only or platform-specific option as such.
• Do not silently change settings that affect release runtime performance (codegen-units, lto, opt-level in [profile.release]); state the tradeoff and get agreement.
• Re-measure after applying changes and report before/after numbers.