ppc64le timeouts

[ax3l]

Currently, there is no way to increase the 50min build time for ppc64le.
Besides trying to reduce the build time on the app time with long-term build variant unification for geometries, splitting out AMReX in its own package (with many, many incompatible build variants) there is another way:

Cross-compile from x86 via setting the build platform: https://conda-forge.org/docs/maintainer/conda_forge_yml.html?highlight=cross%20compile#build-platform

Example feedstock doing this: https://github.com/conda-forge/clangdev-feedstock

[ax3l]

Implementing cross-compilation needs PRs to BLAS++ and LAPACK++, which currently have try_run components in their build logic that does not work out-of-the-box for cross-compilation workflows.

[ax3l]

Solved via #33