cargo-n64 llvm_asm error.txt

$ cargo n64 build --ipl3 ./ipl3.bin --package hello-ipl3font
    Building with cargo xbuild
    Updating crates.io index
   Compiling compiler_builtins v0.1.28
   Compiling core v0.0.0 (/Users/me/.rustup/toolchains/nightly-2020-02-16-x86_64-apple-darwin/lib/rustlib/src/rust/src/libcore)
   Compiling rustc-std-workspace-core v1.99.0 (/Users/me/.rustup/toolchains/nightly-2020-02-16-x86_64-apple-darwin/lib/rustlib/src/rust/src/tools/rustc-std-workspace-core)
error[E0635]: unknown feature `llvm_asm`
 --> /Users/me/.cargo/registry/src/github.com-1ecc6299db9ec823/compiler_builtins-0.1.28/src/lib.rs:3:12
  |
3 | #![feature(llvm_asm)]
  |            ^^^^^^^^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0635`.
error: could not compile `compiler_builtins`.
warning: build failed, waiting for other jobs to finish...
error: build failed
error: `"/Users/me/.rustup/toolchains/nightly-2020-02-16-x86_64-apple-darwin/bin/cargo" "rustc" "-p" "alloc" "--release" "--manifest-path" "/var/folders/j3/7pf540td3xncn7jdqtb62_ph00058y/T/xargo.4HKdojRIwIpQ/Cargo.toml" "--target" "/var/folders/j3/7pf540td3xncn7jdqtb62_ph00058y/T/n64-build/mips-nintendo64-none.json" "--" "-Z" "force-unstable-if-unmarked"` failed with exit code: Some(101)
note: run with `RUST_BACKTRACE=1` for a backtrace
error: Build error
caused by: Subcommand failed
caused by: Command failed with exit code: Some(1)

$ rustc --version
rustc 1.43.0-nightly (61d9231ff 2020-02-15)

$ rustup --version
rustup 1.21.1 (2020-01-08)

$ rustup show
Default host: x86_64-apple-darwin
rustup home:  /Users/me/.rustup

installed toolchains
--------------------

nightly-2020-02-16-x86_64-apple-darwin
nightly-x86_64-apple-darwin

active toolchain
----------------

nightly-2020-02-16-x86_64-apple-darwin (overridden by '/Users/me/cargo-n64/rust-toolchain')
rustc 1.43.0-nightly (61d9231ff 2020-02-15)