…t permissionsThe Arduino Boards Manager automatically executes the `post_install.sh` script during installation of the platform on aLinux machine.This platform's post-install script is intended to create a udev rules file that gives write permissions for the USBdevices of the platform's boards. These permissions are required in order to upload to the boards.The creation of the udev rules file requires superuser privileges, which are typically not available in the context ofthe post-install script's execution. The script contains code to check whether the necessary privileges are available.If not, it prints a message and skips the udev rules file creation.Previously the message printed when the udev rules file creation was not possible was "Please run as root". This messagewas completely meaningless to the user when printed during the Boards Manager installation. Worse, it might cause themto think they must run the Arduino development software as root user, which is a bad idea and also wouldn't result inthe udev rules file being created since the installation of the platform to the user's account was already completed.The message is hereby updated to provide a meaningful explanation of the potential problem as well as the specificcommand the user can run from the terminal to execute the script as superuser.

… on Linux machineThe Arduino Boards Manager automatically executes the `post_install.sh` script during installation of the platform on anon-Windows machine.The platform's post-install script is Linux-specific, but no provisions were made in the script code for the fact thatit is also executed on macOS machines. Previously, this was fairly innocuous because, although misleading, the messageprinted to the output during the platform installation was short and cryptic and thus easy for the average macOS user toignore:```Configuring platform.Please run as root```Since it is important for Linux users to manually run the script and the previous message did not effectivelycommunicate that, the script was recently modified to print helpful instructions during the Boards Manager installation.The fact that the script is also executed on macOS machines was not considered in that work. This meant that, althoughan improvement for the Linux user experience was accomplished, the macOS user experience was worsened because thoseusers were then presented with more prominent and detailed inappropriate instructions. For example:```Configuring platform.You might need to configure permissions for uploading.To do so, run the following command from the terminal:sudo "/Users/per/Library/Arduino15/packages/arduino/hardware/TODO/42.0.0/post_install.sh"```The problem is fixed by adjusting the script so that the script simply returns silently if it is invoked on a non-Linuxmachine. macOS users will now only see the following benign message in the output during the Boards Managerinstallation:```Configuring platform.```The POSIX-compliant shell code for determining the operating system the script is running under was derived from theArduino CLI application's cross-platform installation script, which has withstood the test of time after years of use bya large user base.

The file permissions were not correctly configured at the time the script was created.