There's a merged pull request on the void-packages repository

portage: update to 3.0.21.
https://github.com/void-linux/void-packages/pull/32385

Description:
#### Have the results of the proposed changes been tested?
- [x] I generally don't use the affected packages but briefly tested this PR

#### Does it build and run successfully? 
- [x] I built this PR locally for my native architecture, (x86_64-glibc)
- [x] I built this PR locally for these architectures (if supported. mark crossbuilds):
  - [x] aarch64-musl
  - [x] armv7l
  - [x] armv6l-musl