Cannot use `#[lang = "start"]` on playground

I am shocked - shocked! - to find that no one has tried this before. https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=08a07ced4b7ba6afcdf8a4bd68487015

error[E0152]: found duplicate lang item `start`
 --> src/lib.rs:7:1
  |
7 | fn _start() {
  | ^^^^^^^^^^^
  |
  = note: the lang item is first defined in crate `std`.
  = note: first definition in `std` loaded from /playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libstd-7edd956e9d8d05ea.rlib
  = note: second definition in the local crate (`playground`)

I expect you're passing --extern std=/playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/lib/libstd-7edd956e9d8d05ea.rlib or something like that. I don't have suggestions for fixing it, this is just to vex you that sysroots are painful. Others must share my pain!!

Start by reproducing the example from the linked Rust Playground URL and inspect the compilation invocation, particularly whether std is passed through --extern. Trace how playground builds nightly programs using #[lang = "start"]. Done means the example no longer reports a duplicate lang item while normal playground compilation continues to work.