===> Building for c2rust-0.15.0
   Compiling c2rust-ast-builder v0.15.0 (/scratch/wip/c2rust/work/c2rust-0.15.0/c2rust-ast-builder)
   Compiling fake-simd v0.1.2
   Compiling strum v0.16.0
   Compiling json v0.12.0
   Compiling pulldown-cmark v0.2.0
   Compiling dtoa v0.4.4
   Compiling diff v0.1.12
   Compiling sequence_trie v0.3.6
error[E0463]: can't find crate for `rustc`
 --> c2rust-ast-builder/src/lib.rs:2:1
  |
2 | extern crate rustc;
  | ^^^^^^^^^^^^^^^^^^^ can't find crate

   Compiling slotmap v0.4.0
   Compiling pulldown-cmark v0.6.1
For more information about this error, try `rustc --explain E0463`.
error: could not compile `c2rust-ast-builder` due to previous error
warning: build failed, waiting for other jobs to finish...
error[E0554]: `#![feature]` may not be used on the stable release channel
 --> /scratch/wip/c2rust/work/vendor/slotmap-0.4.0/src/lib.rs:4:35
  |
4 | #![cfg_attr(feature = "unstable", feature(untagged_unions, try_reserve))]
  |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

For more information about this error, try `rustc --explain E0554`.
error: build failed
*** Error code 101

