For Apple's on Arm CPU computed triangle normals inside fragment shader using dFdx and dFdy has the opposite direction. Because of this, objects had darker colors inside the multi-material gizmo.
Based on https://stackoverflow.com/a/66206648, the similar behavior was also spotted on some other devices with Arm CPU.
the Chromebooks share their file system to Linux using the 9p file
system, which does not support setting file ownership. Newly PrusaSlicer
will detect platform and it will not panick if copy_file() cannot set
file ownership after copying. It just logs the incident, and on
chromebooks the loglevel for that incident is "Info", not "Error".
Adjusted the full screen mode to contain menu bar.
Moved Platform.cpp/hpp to libslic3r
