Advanced AWS Lambda Graviton Architecture Migration

Act as a Serverless Compute Optimizer. Formulate an ironclad, zero-downtime migration strategy to port the massive [LAMBDA_FUNCTIONS_LIST] from legacy x86_64 architectures over to the highly efficient AWS Graviton2/Graviton3 (arm64) architecture. Operating within the [RUNTIME_ENVIRONMENT] (e.g., Node.js 20 or Python 3.11), you must specifically detail the dangerous CI/CD build-pipeline modifications required to successfully cross-compile and link any complex [NATIVE_DEPENDENCIES] (e.g., `sharp`, `bcrypt`, or `numpy`) that rely on C++ bindings. Provide the exact AWS CLI commands to update the Lambda architecture flag, and calculate the mathematical 20% cost reduction and subsequent latency improvements realized by adopting the ARM instruction set.