Error: fork/exec /var/task/bootstrap: no such file or directory

[RichardChester]

🐛 Bug description

I am currently building my rust lambda using the dockerless method, it builds and deploys fine but when I attempt to test it throws the error:
Error: fork/exec /var/task/bootstrap: no such file or directory Runtime.InvalidEntrypoint

🤔 Expected Behavior

it should execute the task inside the lambda as normal

👟 Steps to reproduce

Using these dependencies

[dependencies]
lambda_runtime = "0.3"
tokio = "1.3.0"
serde = "1.0.116"
serde_json = "1.0.56"
tokio-postgres = {version = "0.5.1", features = ["with-chrono-0_4"]}
rusoto_secretsmanager = "0.46.0"
lazy_static = "1.2"
chrono = "0.4.19"
rust_decimal = { version = "1.10.3", features = ["db-tokio-postgres"] }
simple_logger = "1.11.0"
log = "0.4.14"
rusoto_sqs = "0.46"
rusoto_core = "0.46"

and code that resembles

#[tokio::main] 
async fn main() -> Result<(), Error> {
    lambda_runtime::run(handler_fn(custom)).await?;
    Ok(()) 
}   

async fn custom(event: Value , _:Context) -> Result<Value,Error> { 
// some code
}

you should be able to reproduce

🌍 Your environment

running on ubuntu with

serverless version: 2.35

rust-plugin version: 0.3.8