Auto merge of #8094 - Freax13:fix-target, r=ehuss

Fix target for doc test cross compilation

- for target paths `Compilation::target` only contains the shortened file name, but we need to pass the full path to rustdoc

src/cargo/ops/cargo_test.rs

@@ -1,6 +1,6 @@
 use std::ffi::OsString;
 
-use crate::core::compiler::{Compilation, Doctest};
+use crate::core::compiler::{Compilation, CompileKind, Doctest};
 use crate::core::shell::Verbosity;
 use crate::core::Workspace;
 use crate::ops;
@@ -163,7 +163,10 @@ fn run_doc_tests(
             .arg(&target.crate_name());
 
         if doctest_xcompile {
-            p.arg("--target").arg(&compilation.target);
+            if let CompileKind::Target(target) = options.compile_opts.build_config.requested_kind {
+                // use `rustc_target()` to properly handle JSON target paths
+                p.arg("--target").arg(target.rustc_target());
+            }
             p.arg("-Zunstable-options");
             p.arg("--enable-per-target-ignores");
         }

tests/testsuite/custom_target.rs

@@ -51,6 +51,12 @@ fn custom_target_minimal() {
     p.cargo("build --lib --target custom-target.json -v").run();
     p.cargo("build --lib --target src/../custom-target.json -v")
         .run();
+
+    // Ensure that the correct style of flag is passed to --target with doc tests.
+    p.cargo("test --doc --target src/../custom-target.json -v -Zdoctest-xcompile")
+        .masquerade_as_nightly_cargo()
+        .with_stderr_contains("[RUNNING] `rustdoc [..]--target [..]foo/custom-target.json[..]")
+        .run();
 }
 
 #[cargo_test]