Use arduino-cli for Travis CI build

Use arduino-cli instead of the Arduino IDE for the Travis CI build.

arduino-cli does not result in the many "SocketListener" warnings that end up interspersed with the compilation output when using the Arduino IDE with Travis CI. These warnings make it more likely that Travis CI's maximum job length will be exceeded, resulting in an errored job. The warnings also make the build log hard to read.

Due to a smaller download size, using arduino-cli results in a shorter CI build duration.

Author: per1234

Diff for: .travis.yml

@@ -1,7 +1,7 @@
 language: generic
 env:
   global:
-    - IDE_VERSION=1.8.9
+    - CLI_VERSION=latest
 matrix:
   include:
     - env:
@@ -42,23 +42,26 @@ matrix:
         - codespell --skip="${TRAVIS_BUILD_DIR}/.git" --ignore-words="${TRAVIS_BUILD_DIR}/extras/codespell-ignore-words-list.txt" "${TRAVIS_BUILD_DIR}"
 # default phases
 before_install:
-  - wget http://downloads.arduino.cc/arduino-$IDE_VERSION-linux64.tar.xz
-  - tar xf arduino-$IDE_VERSION-linux64.tar.xz
-  - mv arduino-$IDE_VERSION $HOME/arduino-ide
-  - export PATH=$PATH:$HOME/arduino-ide
+  - wget http://downloads.arduino.cc/arduino-cli/arduino-cli-$CLI_VERSION-linux64.tar.bz2
+  - tar xf arduino-cli-$CLI_VERSION-linux64.tar.bz2
+  - mkdir -p "$HOME/bin"
+  - mv arduino-cli-*-linux64 $HOME/bin/arduino-cli
+  - export PATH="$PATH:$HOME/bin"
+  - arduino-cli core update-index
   - if [[ "$BOARD" =~ "arduino:samd:" ]]; then
-      arduino --install-boards arduino:samd;
+      arduino-cli core install arduino:samd;
     fi
-  - arduino --install-library ArduinoCloudThing
-  - arduino --install-library ArduinoECCX08
-  - arduino --install-library ArduinoIoTCloudBearSSL
-  - arduino --install-library ArduinoMqttClient
-  - arduino --install-library MKRGSM
-  - arduino --install-library RTCZero
-  - arduino --install-library WiFi101
-  - arduino --install-library WiFiNINA
-  - buildExampleSketch() { arduino --verify --board $BOARD $PWD/examples/$1/$1.ino; }
-  - buildExampleUtilitySketch() { arduino --verify --board $BOARD $PWD/examples/utility/$1/$1.ino; }
+  - arduino-cli lib install ArduinoCloudThing
+  - arduino-cli lib install ArduinoECCX08
+  - arduino-cli lib install ArduinoIoTCloudBearSSL
+  - arduino-cli lib install ArduinoMqttClient
+  - arduino-cli lib install MKRGSM
+  - arduino-cli lib install RTCZero
+  - arduino-cli lib install WiFi101
+  - arduino-cli lib install WiFiNINA
+  - arduino-cli lib install Ethernet
+  - buildExampleSketch() { arduino-cli compile --warnings all --fqbn $BOARD $PWD/examples/$1; }
+  - buildExampleUtilitySketch() { arduino-cli compile --warnings all --fqbn $BOARD $PWD/examples/utility/$1; }
 install:
   - mkdir -p $HOME/Arduino/libraries
   - ln -s $PWD $HOME/Arduino/libraries/.