Support for aarch64 was recencly added in fpc.
This regenerate the Makefile to include aarch64 support as the one in
the repository was too old to include it.
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.
Ram Kromberg