Fix Travis build

Author: igrr

.travis.yml

@@ -34,7 +34,7 @@ script:
   - source tests/common.sh
   - arduino --board esp8266com:esp8266:generic --save-prefs
   - arduino --get-pref sketchbook.path
-  - build_sketches arduino $ESP8266_ARDUINO_DIR/libraries/ESP8266WiFi/examples/HTTPSRequest
+  - build_sketches $HOME/arduino_ide $ESP8266_ARDUINO_DIR/libraries/ESP8266WiFi/examples/HTTPSRequest
   # Feel free to add more test cases (for other environments) here
 
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