message: Update documentation for custom target dependencies.
diff: @@ -114,7 +114,24 @@ fn basic() {
  #[cargo_test(build_std)]
  fn cross_custom() {
  let p = project()
  - .file("src/lib.rs", "#![no_std] pub fn f() {}")
  + .file(
  + "Cargo.toml",
  + r#"
  + [package]
  + name = "foo"
  + version = "0.1.0"
  + edition = "2018"
  +
  + [target.custom-target.dependencies]
  + dep = { path = "dep" }
  + "#,
  + )
  + .file(
  + "src/lib.rs",
  + "#![no_std] pub fn f() -> u32 { dep::answer() }",
  + )
  + .file("dep/Cargo.toml", &basic_manifest("dep", "0.1.0"))
  + .file("dep/src/lib.rs", "#![no_std] pub fn answer() -> u32 { 42 }")
  .file(
  "custom-target.json",
  r#"
  