Fix typo in compile.rs

src/bootstrap/compile.rs

@@ -2,7 +2,7 @@
 //! library.
 //!
 //! This module contains some of the real meat in the rustbuild build system
-//! which is where Cargo is used to compiler the standard library, libtest, and
+//! which is where Cargo is used to compile the standard library, libtest, and
 //! compiler. This module is also responsible for assembling the sysroot as it
 //! goes along from the output of the previous stage.