ArduinoCDT 181 Cookbook
Back Ground
Running Eclipse + ArduinoCDT plugin on MacOS up to 10.13.6 (High Sierra) was running fine upto version 1.6.3 of the Arduino AVR Boards. Upgrade to version 1.8.1 of the Arduino AVR boards failed. Moreover also the Intel Edison boards could not be new installed anymore. Eclipse + ArduinoCdt is running fine on MacOS 10.14.* (Mojave) when upgraded from previous versions. However installing new boards became an issue.
Mayhem MacOS 10.5.* (Catalina) doesn't support 32 bit applications.
With this in mind a mid2011 Mac mini with MacOS 10.3.6 was configured with the .arduincdt directory tree from the Mojave iMac. This provided a working installation with the already installed 1.6.3 version of the Arduino AVR boards and the 1.6.7_1.0 version of the Intel Edison boards.
Upgrade AVR boards to 1.8.1
The Arduino EDI has the 1.8.1 Arduino Avr Board installed by default. So how about just copying the configuration files over. The issue is that the default install of the Arduino.app has the configuration files installed in the app in a different structure as used in the ArduinoCDT.
ArduinoCDT
.arduinCDT/packages/arduino/hardware/avr/{version}/*
/tools
v.s. Arduino.app
Arduino.app/Contents/Java/hardware/arduino/*
/tools/avr/bin/*
So approach is to duplicate the 1.6.3 folder, rename it 1.8.1 and then copy the specific files version 1.8.1 files over from the Arduino.app.