Package refuses to build with current GCC (11), but building with older
GCC causes error linking libminc and I don't want to pin a bunch of
deps.
A newer version is available upstream but it only works with ITK 5.0
(see https://github.com/BIC-MNI/EZminc/issues/15),
but we have 4.x and 5.2.x in tree and I'm reluctant to add 5.0 just for
one package (even ITK 4.x is only used by ants and ezminc and should be
removed as soon as ants is upgraded).
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.
