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.
These packages should in theory work with our GCC toolchains, but
there are some definite breakages that need to be tracked down.
Comparing output of these to old gcc-arm-embedded is important.
Affected packages include:
- axolooti
- avrdudess
- opentx
- microscheme
- betaflight
- inav
- blackmagic
- simavr
- gnuk
