Rollup merge of rust-lang#95836 - workingjubilee:doctest-exe, r=notriddle

Use rust_out{,.exe,.wasm} for doctests

This was mentioned as an issue to me by `@bruxisma.` There are 3 separate instances where "rust_out" can become part of the name of a Rust executable, so I am mostly just hoping that this fixes the problem, given that the other sites which it can slip in seem to be well-behaved.

Author: Dylan-DPC

src/librustdoc/doctest.rs

@@ -310,7 +310,10 @@ fn run_test(
     let (test, line_offset, supports_color) =
         make_test(test, Some(crate_name), lang_string.test_harness, opts, edition, Some(test_id));
 
-    let output_file = outdir.path().join("rust_out");
+    // Make sure we emit well-formed executable names for our platform.
+    let mut output_file = outdir.path().join("rust_out");
+    output_file.set_extension(env::consts::EXE_EXTENSION);
+    let output_file = output_file;
 
     let rustc_binary = rustdoc_options
         .test_builder