Fix the Travis CI build by accepting the Android SDK licenses

.travis.yml

@@ -1,7 +1,15 @@
 language: android
+env:
+  global:
+    - ANDROID_HOME=/usr/local/android-sdk
 android:
   components:
-    - android-29
-    - build-tools-29.0.2
+  - android-29
+  - build-tools-29.0.2
+before_install:
+  - mkdir -p $ANDROID_HOME/licenses
+  - echo "8933bad161af4178b1185d1a37fbf41ea5269c55" > $ANDROID_HOME/licenses/android-sdk-license
+  - echo "d56f5187479451eabf01fb78af6dfcb131a6481e" >> $ANDROID_HOME/licenses/android-sdk-license
+  - echo "24333f8a63b6825ea9c5514f83c2829b004d1fee" >> $ANDROID_HOME/licenses/android-sdk-license
 script:
-    - ./gradlew build test
+  - ./gradlew build test