rust-polling: Please try to rebuild rust-polling for loong64

[zhangdandan <zhangdandan@loongson.cn>]

Source: rust-polling
Version: 3.4.0-1
Severity: wishlist
Tags: help
User: debian-loongarch@lists.debian.org
Usertags: loong64

Dear maintainers,

The package librust-async-io-2+default-dev blocked compilation of 29 
packages in the Debian Package Auto-Building environment.
The dependency state of rust-async-io is as follows,
```
Dependency installability problem for rust-async-io on loong64:
rust-async-io build-depends on missing:
- librust-polling-3+default-dev:loong64
```
After analyzing the package rust-async-io, I found out that it's because 
compilation of rust-polling failed.
The build log of rust-polling can be found at 
https://buildd.debian.org/status/logs.php?pkg=rust-polling&ver=3.4.0-1&arch=loong64.

I have built the rust-polling successfully in my local loong64 
environment, without modifications required.
```
......
   dh_md5sums -O--buildsystem=cargo
   dh_builddeb -O--buildsystem=cargo
dpkg-deb: building package '../librust-polling-dev_3.4.0-1_loong64.deb' 
in 'librust-polling-dev'。
dpkg-genbuildinfo -O../rust-polling_3.4.0-1_loong64.buildinfo
dpkg-genchanges -O../rust-polling_3.4.0-1_loong64.changes

```
Please try to rebuild rust-polling for loong64 in the Debian Package 
Auto-Building environment.
If you have any questions, you can contact me at any time.

thanks,
Dandan Zhang