Rollup merge of rust-lang#140706 - GuillaumeGomez:fix-missing-temp-dir-cleanup, r=notriddle

[rustdoc] Ensure that temporary doctest folder is correctly removed even if doctests failed

Fixes rust-lang#139899.

The bug was due to the fact that if any doctest fails for any reason, we call `exit` (or it's called inside `libtest` if not edition 2024), meaning that `TempDir`'s destructor isn't called, and therefore the temporary folder isn't cleaned up.

Took me a while to figure out how to reproduce but finally I was able to reproduce the bug with:

`````rust
#![doc(test(attr(deny(warnings))))]

//! ```
//! let a = 12;
//! ```
`````

And then I ensured that panicking doctests were cleaned up as well:

`````rust
//! ```
//! panic!();
//! ```
`````

And finally I checked if it was fixed for merged doctests too (`--edition 2024`).

To make this work, I needed to add a new public function in `libtest` too which would call a function once all tests have been run.

So only issue is: I have absolutely no idea how we can add a regression test for this fix. If anyone has an idea...

r? `@notriddle`

Author: GuillaumeGomez

test/src/lib.rs

@@ -98,6 +98,15 @@ const SECONDARY_TEST_BENCH_BENCHMARKS_VAR: &str = "__RUST_TEST_BENCH_BENCHMARKS"
 // The default console test runner. It accepts the command line
 // arguments and a vector of test_descs.
 pub fn test_main(args: &[String], tests: Vec<TestDescAndFn>, options: Option<Options>) {
+    test_main_with_exit_callback(args, tests, options, || {})
+}
+
+pub fn test_main_with_exit_callback<F: FnOnce()>(
+    args: &[String],
+    tests: Vec<TestDescAndFn>,
+    options: Option<Options>,
+    exit_callback: F,
+) {
     let mut opts = match cli::parse_opts(args) {
         Some(Ok(o)) => o,
         Some(Err(msg)) => {
@@ -151,6 +160,7 @@ pub fn test_main(args: &[String], tests: Vec<TestDescAndFn>, options: Option<Opt
         let res = console::run_tests_console(&opts, tests);
         // Prevent Valgrind from reporting reachable blocks in users' unit tests.
         drop(panic::take_hook());
+        exit_callback();
         match res {
             Ok(true) => {}
             Ok(false) => process::exit(ERROR_EXIT_CODE),