RFC: add pkg-config to base-chroot

[Duncaen]

Its by far the most common hostmakedepends and would avoid having to install/uinstall it every build, has 0 extra dependencies and would avoid having to add it to hostmakedepends manually.

$ find srcpkgs -maxdepth 1 -type d -printf '%f\n' | xe -s './xbps-src show-hostmakedepends $1 > hostmakedepends/$1'
$ sort hostmakedepends/* | uniq -c | sort -nr | head -n10
   3538 pkg-config
   1471 ninja
   1465 python3-packaging-bootstrap
   1465 cmake-bootstrap
   1095 python3-setuptools
   1095 gettext
    972 perl
    796 meson
    745 automake
    636 python3-build

[classabbyamp]

I've looked into this, and the only thing we'd need to handle is setting the alternative to pkgconf for the few things that only work with pkgconf