Improve diagnose for unconditional panic when resource limit

Author: Binlogo

compiler/rustc_interface/src/util.rs

@@ -287,7 +287,15 @@ pub(crate) fn run_in_thread_pool_with_globals<
  pool.install(|| f(current_gcx.into_inner(), proxy))
  },
  )
- .unwrap()
+ .unwrap_or_else(|err| {
+ let mut diag = thread_builder_diag.early_struct_fatal(format!(
+ "failed to spawn compiler thread pool: could not create {threads} threads ({err})",
+ ));
+ diag.help(
+ "try lowering `-Z threads` or checking the operating system's resource limits",
+ );
+ diag.emit();
+ })
  })
  })
 }