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