New comment by Logarithmus on void-packages repository

https://github.com/void-linux/void-packages/pull/30702#issuecomment-833583789

Comment:
> This will blow up once you run parallel builds in different masterdirs. sccache always listens on some tcp port on localhost. You would need to figure out how to either allocate a TCP port per masterdir or implement the communication via unix sockets and upstream it.

I should definitely test this scenario. I still think this PR can be merged in its current state, because `$XBPS_SCCACHE` is turned off by default. Maybe I should add a disclaimer in `README.md` about parallel builds in differrent masterdirs though.