Add testing/github-action for ppc64le

[brifordwylie]

We'd like to have the CI/CD test also cover BIG endian platforms, so we should figure out how to do that with GithubActions.

shrug.. maybe this? https://github.com/uraimo/run-on-arch-action

Related to:

• Adding Power support(ppc64le) with ci and testing to the project for architecture independent #497

[obormot]

We'd like to have the CI/CD test also cover BIG endian platforms

Just for accuracy ppc64le is little endian (what "le" stands for), some big endian platforms are ppc64, s390x