Auto merge of #51756 - nielx:fix/librustdoc, r=GuillaumeGomez

Haiku: set stack size to 16 MB on Haiku, use 32 MB on other platforms

The maximum stack size on Haiku is set to 16 MB (see [the Haiku source](https://git.haiku-os.org/haiku/tree/headers/private/system/thread_defs.h#n17)). With this change rustdoc will also work on Haiku.

Author: bors

src/librustdoc/lib.rs

@@ -103,10 +103,14 @@ struct Output {
 }
 
 pub fn main() {
-    const STACK_SIZE: usize = 32_000_000; // 32MB
+    let thread_stack_size: usize = if cfg!(target_os = "haiku") {
+        16_000_000 // 16MB on Haiku
+    } else {
+        32_000_000 // 32MB on other platforms
+    };
     rustc_driver::set_sigpipe_handler();
     env_logger::init();
-    let res = std::thread::Builder::new().stack_size(STACK_SIZE).spawn(move || {
+    let res = std::thread::Builder::new().stack_size(thread_stack_size).spawn(move || {
         syntax::with_globals(move || {
             get_args().map(|args| main_args(&args)).unwrap_or(1)
         })