Confusing error message when you attempt to build for a target that rustc isn't prepared for

[posix4e]

I am trying to build rustboot

rustc -O --target i686-unknown-linux-gnu --crate-type lib -o main.o --emit obj main.rs

Get's
te-type lib -o main.o --emit obj main.rs
main.rs:7:1: 7:19 error: can't find crate for core
main.rs:7 extern crate core;
^~~~~~~~~~~~~~~~~~

The actual error should tell you that you are trying to build for a target that rustc can't handle.

[brson]

Fixed.