emsdk

Fix support for Apple M1 (#753)

* Fix support for Apple M1. Node.js will still run via Rosetta 2 emulation since they do not yet have M1 support, but Python, LLVM, Emscripten and Binaryen will be native.

* Update M1 python version and URL

* Remove .gitignore additions

* Move python first in the manifest (#441)

* Use macosx-version-min when building python

* Update Intel macOS python package name