error[E0463]: can't find crate for `core` | = note: the `thumbv7em-none-eabihf` target may not be installed = help: consider downloading the target with `rustup target add thumbv7em-none-eabihf`

Received a internal compiler error OR an unknown message type, view this in debug mode to view the payload

{ "rendered": "For more information about this error, try `rustc --explain E0463`.\n", "$message_type": "diagnostic", "children": [], "code": null, "level": "failure-note", "message": "For more information about this error, try `rustc --explain E0463`.", "spans": [] }