message: Fix rare failure in collision_export test.
diff: @@ -91,6 +91,8 @@ This may become a hard error in the future; see <https://github.com/rust-lang/ca
  }
  #[cargo_test]
  +// --out-dir and examples are currently broken on MSVC.
  +// See https://github.com/rust-lang/cargo/issues/7493
  #[cfg(not(target_env = "msvc"))]
  fn collision_export() {
  // `--out-dir` combines some things which can cause conflicts.
  @@ -100,7 +102,9 @@ fn collision_export() {
  .file("src/main.rs", "fn main() {}")
  .build();
  - p.cargo("build --out-dir=out -Z unstable-options --bins --examples")
  + // -j1 to avoid issues with two processes writing to the same file at the
  + // same time.
  + p.cargo("build -j1 --out-dir=out -Z unstable-options --bins --examples")
  .masquerade_as_nightly_cargo()
  .with_stderr_contains("\
  [WARNING] `--out-dir` filename collision.
  