You can specify environment variables for AWS Lambda either using AWS Console or CLI. You can actually use the below code to set up Lambda with an LD_LIBRARY_PATH environment variable using AWS CLI:
aws lambda create-function \
  --region us-east-1
  --function-name myTestFunction
  --zip-file fileb://path/package.zip
  --role role-arn
  --environment Variables={LD_LIBRARY_PATH=/usr/bin/test/lib64}
  --handler index.handler
  --runtime nodejs4.3
  --profile default
You can refer to this - AWS Lambda Environment Variables to know more