Bug#956869: wireguard-dkms missing dependency on bc

[何立新]

```

Build-Depends:
         debhelper-compat (= 12),

         dkms,

+         bc,

         Standards-Version: 4.5.0

```


I'm curious that if adding `bc` to "|Build-Depends: |" instead of  
"|Depends: |" will fix this problem for who don't build package by 
themselves?