[Travis] Explicitly set build flag

.travis.yml

@@ -33,29 +33,37 @@ before_install:
   - if [[ "$BOARD" =~ "arduino:avr:uno" ]]; then
       export BUILD_EXAMPLES=true;
     elif [[ "$BOARD" =~ "arduino:avr:mega" ]]; then
+      export BUILD_EXAMPLES=false;
     elif [[ "$BOARD" =~ "arduino:avr:leonardo" ]]; then
+      export BUILD_EXAMPLES=false;
     elif [[ "$BOARD" =~ "esp8266:esp8266:" ]]; then
+      export BUILD_EXAMPLES=false;
       arduino --pref "http://arduino.esp8266.com/stable/package_esp8266com_index.json" --save-prefs 2>&1;
       arduino --install-boards esp8266:esp8266;
       export SKIP_PAT='(HTTP|MQTT).*ino';
     elif [[ "$BOARD" =~ "esp32:esp32:" ]]; then
+      export BUILD_EXAMPLES=false;
       arduino --pref "https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json" --save-prefs 2>&1;
       arduino --install-boards esp32:esp32;
     elif [[ "$BOARD" =~ "STM32:stm32:" ]]; then
+      export BUILD_EXAMPLES=false;
       arduino --pref "https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json" --save-prefs 2>&1;
       arduino --install-boards STM32:stm32;
     elif [[ "$BOARD" =~ "arduino:samd:" ]]; then
+      export BUILD_EXAMPLES=false;
       arduino --pref "https://github.com/stm32duino/BoardManagerFiles/raw/master/STM32/package_stm_index.json" --save-prefs 2>&1;
       arduino --install-boards arduino:samd;
     elif [[ "$BOARD" =~ "arduino:sam:" ]]; then
+      export BUILD_EXAMPLES=false;
       arduino --install-boards arduino:sam;
     elif [[ "$BOARD" =~ "SparkFun:apollo3:" ]]; then
+      export BUILD_EXAMPLES=false;
       arduino --pref "https://raw.githubusercontent.com/sparkfun/Arduino_Boards/master/IDE_Board_Manager/package_sparkfun_index.json" --save-prefs 2>&1;
       arduino --install-boards SparkFun:apollo3;
     fi
 
   # check if this release commit (or forced build) and if so, build for every board
-  - if [[ "$TRAVIS_COMMIT_MESSAGE" =~ "Bump version to" ] || [ "$TRAVIS_COMMIT_MESSAGE" =~ "TRAVIS_FORCE_BUILD" ]]; then
+  - if [[ "$TRAVIS_COMMIT_MESSAGE" =~ "Bump version to" || "$TRAVIS_COMMIT_MESSAGE" =~ "TRAVIS_FORCE_BUILD" ]]; then
       export BUILD_EXAMPLES=true;
     fi
 
@@ -72,7 +80,7 @@ branches:
 script:
   # build all example sketches
   - |
-    if [ "$BUILD_EXAMPLES" = true ] ; then
+    if [ ! -z "$BUILD_EXAMPLES" ] && [ "$BUILD_EXAMPLES" = true ] ; then
       for example in $(find $PWD/examples -name '*.ino' | sort); do
         # check whether to skip this sketch
         if [ ! -z "$SKIP_PAT" ] && [[ ${example} =~ $SKIP_PAT ]]; then
@@ -91,7 +99,7 @@ script:
         fi
       done
     else
-      echo -e "\n\033[1;33mExample build skipped for $BOARD\033[0m";
+      echo -e "\n\033[1;33mExample builds skipped for $BOARD\033[0m";
     fi
 
   # generate Doxygen documentation (only for Arduino UNO)