Correctly handle should_panic on targets not supporting it

Author: GuillaumeGomez

src/librustdoc/doctest/runner.rs

@@ -266,7 +266,15 @@ fn main() {returns_result} {{
         )
         .unwrap();
     }
-    let not_running = ignore || scraped_test.no_run(opts);
+    let should_panic = scraped_test.langstr.should_panic;
+    // On some platforms, exit code can only be 0 or 1, preventing us to actually know if it's a
+    // panic. In this case, we ignore the tests with `should_panic`.
+    //
+    // Emscripten can catch panics but other wasm targets cannot
+    let ignore_because_no_process_support = should_panic
+        && (cfg!(target_family = "wasm") || cfg!(target_os = "zkvm"))
+        && !cfg!(target_os = "emscripten");
+    let not_running = ignore_because_no_process_support || ignore || scraped_test.no_run(opts);
     writeln!(
         output_merged_tests,
         "
@@ -294,7 +302,6 @@ if let Some(bin_path) = crate::__doctest_mod::doctest_path() {{
     test::assert_test_result(doctest_bundle::{test_id}::__main_fn())
 }}
 ",
-                should_panic = scraped_test.langstr.should_panic,
             )
         },
     )