New review comment by dkosovic on void-packages repository

https://github.com/void-linux/void-packages/pull/23646#discussion_r459121989

Comment:
I like how `${XBPS_CROSS_BASE}`simplified things.

awk version of `PPP_VERSION` ends up being `"2.4.7"` while the sed version didn't have quotes, but `--with-pppd-plugin-dir=/usr/lib/pppd/"2.4.7"` will work fine as a configure argument, so I'm okay with it.