Depends on Arduino-CI/arduino_ci#297.

jgfoster · jgfoster · commit 5fc69df8ed8f · 2021-04-04T14:08:36.000-07:00
diff --git a/.arduino-ci.yml b/.arduino-ci.yml
@@ -1,9 +1,18 @@
 platforms:
   mega2560:
+    board: arduino:avr:mega:cpu=atmega2560
+    package: arduino:avr
     gcc:
+      features:
+      defines:
+        - __AVR__
+        - __AVR_ATmega2560__
+        - ARDUINO_ARCH_AVR
+        - ARDUINO_AVR_MEGA2560
       warnings:
         - no-unknown-attributes
         - no-address-of-packed-member
+      flags:
 
 unittest:
   platforms:
