message: faster zeroing of .bss
diff: @@ -104,10 +104,8 @@ unsafe extern "C" fn rust_start(app_start: usize, stacktop: usize, app_heap_star
  );
  // Zero .bss (specified by the linker script).
  - let bss_end = layout_header.bss_start + layout_header.bss_size; // 1 past the end of .bss
  - for i in layout_header.bss_start..bss_end {
  - core::ptr::write(i as *mut u8, 0);
  - }
  + let bss_start = layout_header.bss_start as *mut u8;
  + core::ptr::write_bytes(bss_start, 0u8, layout_header.bss_size);
  // TODO: Wait for rustc to have working ROPI-RWPI relocation support, then
  // implement dynamic relocations here. At the moment, rustc does not have
  