Add rustdoc-ui regression test for rust-lang#140289

Author: GuillaumeGomez

tests/rustdoc-ui/doctest/stdout-and-stderr.rs

@@ -0,0 +1,26 @@
+// This test ensures that the output is correctly generated when the
+// doctest fails. It checks when there is stderr and stdout, no stdout
+// and no stderr/stdout.
+//
+// This is a regression test for <https://github.com/rust-lang/rust/issues/140289>.
+
+//@ edition: 2024
+//@ compile-flags:--test --test-args=--test-threads=1
+//@ normalize-stdout: "tests/rustdoc-ui/doctest" -> "$$DIR"
+//@ normalize-stdout: "finished in \d+\.\d+s" -> "finished in $$TIME"
+//@ normalize-stdout: "panicked at .+rs:" -> "panicked at $$TMP:"
+//@ failure-status: 101
+//@ rustc-env:RUST_BACKTRACE=0
+
+//! ```
+//! println!("######## from a DOC TEST ########");
+//! assert_eq!("doc", "test");
+//! ```
+//!
+//! ```
+//! assert_eq!("doc", "test");
+//! ```
+//!
+//! ```
+//! std::process::exit(1);
+//! ```

tests/rustdoc-ui/doctest/stdout-and-stderr.stdout

@@ -0,0 +1,46 @@
+
+running 3 tests
+test $DIR/stdout-and-stderr.rs - (line 15) ... FAILED
+test $DIR/stdout-and-stderr.rs - (line 20) ... FAILED
+test $DIR/stdout-and-stderr.rs - (line 24) ... FAILED
+
+failures:
+
+---- $DIR/stdout-and-stderr.rs - (line 15) stdout ----
+Test executable failed (exit status: 101).
+
+stdout:
+######## from a DOC TEST ########
+
+stderr:
+
+thread 'main' panicked at $TMP:7:1:
+assertion `left == right` failed
+  left: "doc"
+ right: "test"
+note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+
+
+---- $DIR/stdout-and-stderr.rs - (line 20) stdout ----
+Test executable failed (exit status: 101).
+
+stderr:
+
+thread 'main' panicked at $TMP:15:1:
+assertion `left == right` failed
+  left: "doc"
+ right: "test"
+note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+
+
+---- $DIR/stdout-and-stderr.rs - (line 24) stdout ----
+Test executable failed (exit status: 1).
+
+
+failures:
+    $DIR/stdout-and-stderr.rs - (line 15)
+    $DIR/stdout-and-stderr.rs - (line 20)
+    $DIR/stdout-and-stderr.rs - (line 24)
+
+test result: FAILED. 0 passed; 3 failed; 0 ignored; 0 measured; 0 filtered out; finished in $TIME
+