Add build for ppc64le

[jennydaman]

pixi (neither micromamba nor uv) provide container images for linux/ppc64le. In this PR, a solution for building for ppc64le is added:

1. Run pixi project export ... to produce a conda spec
2. Run micromamba create ... to produce conda environments for the target platforms
3. Run pixi run build (which calls hatch) to produce a wheel for pfcon
4. Copy the conda environment and pfcon-*.whl into images and build

There is also an added benefit: by running the package manager on the host instead of in docker build, it is faster (compared to running the package manager during docker build using QEMU).