> Adapted from rust-lang#11183

Previously, `is_dep_activated` depends on `activated_dependencies`,
which is a map of `PackageFeaturesKey` to its own activated `DepFeature`s.
`PackageFeaturesKey` in feature resolver is always comprised of

* A `PackageId` of a given dependency, and
* A enum value that helps decoupling activated features for that dependency.
  Currently depending on the type of given dependency.

Looking into issue 10526, it has an `activated_dependencies` of

```
{
    (mycrate, NormalOrDev) -> [dep:mybindep]
}
```

However, this [line][1] accidentally use a parent's `pkgid`
and a dependency's `FeaturesFor` to compose a key:

```
(mycrate, ArtifactDep("x86_64-unknown-linux-gnu"))
```

That is never a valid key to query features for artifacts dependency.
A valid key should be comprised of components both from the parent:

```
(mycrate, NormalOrDev)
```

Or both from the dependency itself:

```
(mybindep, ArtifactDep("x86_64-unknown-linux-gnu"))
```

This `unit_for` is from parent and should already contain its own
artifact dep information inside `artifact_target_for_features`,
so we don't need to map any dependency artifact from `dep.artifact()`.

[1]: https://github.com/rust-lang/cargo/blob/a2ea66bea6fe8156444144e98911d073d56c2c0c/src/cargo/core/compiler/unit_dependencies.rs#L1106-L1107

`{ …, artifact = "bin", target = "target" }` should also be considered
to being built for `FeaturesFor::ArtifactDep` instead of `NormalOrDev`.

[This line][1] requests for `ArtifactDep` but [here][2] Cargo ignore
assumed host target of artifact dep.

Change it to explicit set host target triple when

- `{ …, target = "target" }`, and
- `--target` is not presented, meaning it would be build on host platform.

[1]: https://github.com/rust-lang/cargo/blob/1382b44e431f58199afdffc2b757962b0e163602/src/cargo/core/compiler/unit_dependencies.rs#L887
[2]: https://github.com/rust-lang/cargo/blob/1382b44e431f58199afdffc2b757962b0e163602/src/cargo/core/resolver/features.rs#L857