Add sched_threads rt function to get the number of scheduler threads

src/rt/rust_builtin.cpp

@@ -863,6 +863,11 @@ set_min_stack(rust_task *task, uintptr_t stack_size) {
     g_custom_min_stack_size = stack_size;
 }
 
+extern "C" CDECL int
+sched_threads(rust_task *task) {
+    return task->kernel->num_threads;
+}
+
 //
 // Local Variables:
 // mode: C++

src/rt/rust_kernel.h

@@ -16,8 +16,6 @@ public:
 private:
     lock_and_signal _kernel_lock;
 
-    const size_t num_threads;
-
     array_list<rust_scheduler *> threads;
 
     randctx rctx;
@@ -30,10 +28,10 @@ private:
 
 public:
 
+    const size_t num_threads;
     int rval;
 
     volatile int live_tasks;
-
     struct rust_env *env;
 
     rust_kernel(rust_srv *srv, size_t num_threads);

src/rt/rustrt.def.in

@@ -38,6 +38,7 @@ rust_run_program
 rust_start
 rust_getcwd
 set_min_stack
+sched_threads
 size_of
 squareroot
 str_alloc