fix(bindeps): assumed host target and optional = true coexist

`{ …, 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

Author: weihanglo

src/cargo/core/resolver/features.rs

@@ -853,12 +853,14 @@ impl<'a, 'cfg> FeatureResolver<'a, 'cfg> {
                                     ArtifactTarget::BuildDependencyAssumeTarget => self
                                         .requested_targets
                                         .iter()
-                                        .filter_map(|kind| match kind {
-                                            CompileKind::Host => None,
-                                            CompileKind::Target(target) => {
-                                                Some(FeaturesFor::ArtifactDep(*target))
+                                        .map(|kind| match kind {
+                                            CompileKind::Host => {
+                                                let host_triple = self.target_data.rustc.host;
+                                                CompileTarget::new(&host_triple).unwrap()
                                             }
+                                            CompileKind::Target(target) => *target,
                                         })
+                                        .map(FeaturesFor::ArtifactDep)
                                         .collect(),
                                 }),
                             )

tests/testsuite/artifact_dep.rs

@@ -2399,7 +2399,6 @@ fn with_target_and_optional() {
 
 #[cargo_test]
 fn with_assumed_host_target_and_optional_build_dep() {
-    // This exercises an incorrect behaviour got to be fixed by the following commit.
     let p = project()
         .file(
             "Cargo.toml",
@@ -2435,8 +2434,16 @@ fn with_assumed_host_target_and_optional_build_dep() {
 
     p.cargo("check -Z bindeps -F d1 -v")
         .masquerade_as_nightly_cargo(&["bindeps"])
-        .with_status(101)
-        .with_stderr_contains("[ERROR] failed to run custom build command for `foo v0.0.1 ([..])`")
-        .with_stderr_contains("[..]thread '[..]' panicked at 'called `Result::unwrap()`[..]")
+        .with_stderr_unordered(
+            "\
+[COMPILING] foo v0.0.1 ([CWD])
+[COMPILING] d1 v0.0.1 ([CWD]/d1)
+[RUNNING] `rustc --crate-name build_script_build [..]--crate-type bin[..]
+[RUNNING] `rustc --crate-name d1 [..]--crate-type bin[..]
+[RUNNING] `[CWD]/target/debug/build/foo-[..]/build-script-build`
+[RUNNING] `rustc --crate-name foo [..]--cfg[..]d1[..]
+[FINISHED] dev [..]
+",
+        )
         .run();
 }