- fix PowerPC architecture detection

[SSE4]

Signed-off-by: SSE4 tomskside@gmail.com

related to the bincrafters/community#443
properly detects ppc64le architecture and few others
based on python's platform.machine(), which actually uses uname under the hood
tested on PowerPC VM
see also

1. https://stackoverflow.com/questions/45125516/possible-values-for-uname-m
2. https://en.wikipedia.org/wiki/Uname
3. https://github.com/gcc-mirror/gcc/blob/master/config.guess

• Refer to the issue that supports this Pull Request.
• If the issue has missing info, explain the purpose/use case/pain/need that covers this Pull Request.
• I've read the Contributing guide.
• I've followed the PEP8 style guides for Python code.
• I've opened another PR in the Conan docs repo to the develop branch, documenting this one. Also adding a description of the changes in the changelog.rst file. https://github.com/conan-io/docs

Changelog: Fix: More complete architecture list in the detection of the gnu triplet and the detection of the build machine architecture.

[SSE4]

also related to the #3449