cargo hangs for 20 more seconds after showing the compilation errors, for apparently no reason

[ghost]

When there are compilation errors, cargo hangs for 20 more seconds after showing them:

$ time cargo run -v
   Compiling phrases v0.0.1 (file:///home/zazdxscf/build/1nonpkgs/rustLearnage/rust_book/phrases)
     Running `rustc src/main.rs --crate-name phrases --crate-type bin -g --out-dir /home/zazdxscf/build/1nonpkgs/rustLearnage/rust_book/phrases/target/debug --emit=dep-info,link -L dependency=/home/zazdxscf/build/1nonpkgs/rustLearnage/rust_book/phrases/target/debug -L dependency=/home/zazdxscf/build/1nonpkgs/rustLearnage/rust_book/phrases/target/debug/deps --extern phrases=/home/zazdxscf/build/1nonpkgs/rustLearnage/rust_book/phrases/target/debug/libphrases.rlib`
src/main.rs:8:5: 8:12 error: expected one of `.`, `;`, `}`, or an operator, found `println`
src/main.rs:8     println!("Hello in English: {}", greetings::hello());
                  ^~~~~~~
Could not compile `phrases`.

Caused by:
  Process didn't exit successfully: `rustc src/main.rs --crate-name phrases --crate-type bin -g --out-dir /home/zazdxscf/build/1nonpkgs/rustLearnage/rust_book/phrases/target/debug --emit=dep-info,link -L dependency=/home/zazdxscf/build/1nonpkgs/rustLearnage/rust_book/phrases/target/debug -L dependency=/home/zazdxscf/build/1nonpkgs/rustLearnage/rust_book/phrases/target/debug/deps --extern phrases=/home/zazdxscf/build/1nonpkgs/rustLearnage/rust_book/phrases/target/debug/libphrases.rlib` (exit code: 101)

real    0m23.901s
user    0m23.303s
sys 0m0.290s

It hangs right on the line before displaying Could not compile phrases.

vs no errors:

$ time cargo run -v
   Compiling phrases v0.0.1 (file:///home/zazdxscf/build/1nonpkgs/rustLearnage/rust_book/phrases)
     Running `rustc src/main.rs --crate-name phrases --crate-type bin -g --out-dir /home/zazdxscf/build/1nonpkgs/rustLearnage/rust_book/phrases/target/debug --emit=dep-info,link -L dependency=/home/zazdxscf/build/1nonpkgs/rustLearnage/rust_book/phrases/target/debug -L dependency=/home/zazdxscf/build/1nonpkgs/rustLearnage/rust_book/phrases/target/debug/deps --extern phrases=/home/zazdxscf/build/1nonpkgs/rustLearnage/rust_book/phrases/target/debug/libphrases.rlib`
     Running `target/debug/phrases`
Hello in English: Hello!
Goodbye in English: Goodbye.
Hello in Japanese: こんにちは
Goodbye in Japanese(日本語): さようなら

real    0m1.729s
user    0m1.200s
sys 0m0.333s

The tested project is here: https://github.com/zazdxscf/rustLearnage/tree/cd3ade8eae6f6cde99e7e750490b2672a1247b54/rust_book/phrases
But works on any, even simpler main.rs ones.

[ghost]

Nevermind, it's actually rustc which hangs!

$ time rustc src/main.rs --crate-name phrases --crate-type bin -g --out-dir /home/zazdxscf/build/1nonpkgs/rustLearnage/rust_book/phrases/target/debug --emit=dep-info,link -L dependency=/home/zazdxscf/build/1nonpkgs/rustLearnage/rust_book/phrases/target/debug -L dependency=/home/zazdxscf/build/1nonpkgs/rustLearnage/rust_book/phrases/target/debug/deps --extern phrases=/home/zazdxscf/build/1nonpkgs/rustLearnage/rust_book/phrases/target/debug/libphrases.rlib
src/main.rs:8:5: 8:12 error: expected one of `.`, `;`, `}`, or an operator, found `println`
src/main.rs:8     println!("Hello in English: {}", greetings::hello());
                  ^~~~~~~

real    0m23.389s
user    0m23.000s
sys 0m0.213s

EDIT: even simple, hangs:

$ time rustc src/main.rs
src/main.rs:8:5: 8:12 error: expected one of `.`, `;`, `}`, or an operator, found `println`
src/main.rs:8     println!("Hello in English: {}", greetings::hello());
                  ^~~~~~~

real    0m23.481s
user    0m23.103s
sys 0m0.193s

$ rustc --version --verbose
rustc 1.5.0-dev (04e497c00 2015-10-24)
binary: rustc
commit-hash: 04e497c0056aed899cd6edbc98e7a68a9b391c5c
commit-date: 2015-10-24
host: x86_64-unknown-linux-gnu
release: 1.5.0-dev