New review comment by Logarithmus on void-packages repository

https://github.com/void-linux/void-packages/pull/31811#discussion_r675992917

Comment:
> It's exported from outside. You can change there, though.

I've just found out that `disable_parallel_build` sets `XBPS_MAKEJOBS=1`. Maybe we don't need `disable_parallel_check` altogether? Otherwise in order for everything to work as expected we should revise `disable_parallel_build` to not mess with `XBPS_MAKEJOBS`, because currently `disable_parallel_build` also implies `disable_parallel_check`, which isn't obvious.
https://github.com/void-linux/void-packages/blob/90243383a366d6dc64c51555cfd4f3a63dd7995c/common/xbps-src/shutils/common.sh#L468-L469