message: add dummy implementations for context switches
  only necessary in test environments
diff: @@ -71,6 +71,12 @@ pub use crate::arch::x86_64::kernel::{
  get_processor_count, message_output_init, output_message_buf, output_message_byte,
  };
  +#[cfg(test)]
  +pub fn switch_to_task(_old_stack: *mut usize, _new_stack: usize) {}
  +#[cfg(test)]
  +pub fn switch_to_fpu_owner(_old_stack: *mut usize, _new_stack: usize) {}
  +
  +#[cfg(not(test))]
  extern "C" {
  pub fn switch_to_task(old_stack: *mut usize, new_stack: usize);
  pub fn switch_to_fpu_owner(old_stack: *mut usize, new_stack: usize);
  