As part of supporting Apple Silicon, we've got to upgrade our embedded
Python to a version that comes with an Apple Silicon build. Python 3.9
suffices. This means we ignore python3.9 while fixing up bundles.
Apple requires all code to be signed on Apple Silicon. We've added signing
to the build. This has to be run after anything that adds to or modifies
the installed files. As of Cmake 3.14 (CMP0082), the install rules are run
in the order declared, so we are able to do this just by adding the
signing subdirectory last in the main CMakeLists.txt. By default, the
build will be signed "ad hoc", which does not require a developer to
create keys or get keys from Apple. We added some CMake variables to
control signing, KICAD_OSX_CODESIGN and KICAD_OSX_SIGNING_*.
In order to better support development, we've added some necessary cleanup
steps to KiCad that were performed externally in the release and nightly
build process, like removing any .pyc files and extra Python symlinks
erroneously introduced by fixup_bundle. We also adjusted "refix_rpaths" to
be more accurate. We should not need "wrangle_bundle" when building and
installing a local development copy of KiCad.