continuation of #109595
pkgconfig was aliased in 2018, however, it remained in
all-packages.nix due to its wide usage. This cleans
up the remaining references to pkgs.pkgsconfig and
moves the entry to aliases.nix.
python3Packages.pkgconfig remained unchanged because
it's the canonical name of the upstream package
on pypi.
* update two explicit references to jdk14 to just jdk, which no longer
points at jdk8 after #89731.
* patch an explicit -XX:+UseConcMarkSweepGC to -XX:UseG1GC, as the
former now throws an error (after having been deprecated since jdk 9)
Jonathan Ringer
Matt McHenry