Fixing preview licence in travis

Author: kevalpatel2106

.travis.yml

@@ -33,7 +33,7 @@ before_script:
 install:
     - echo y | android update sdk -u -a -t tools
     - echo y | android update sdk -u -a -t platform-tools
-    - echo y | android update sdk -u -a -t build-tools-28.0.0-rc1
+    - echo y | android update sdk -u -a -t build-tools;28.0.0-rc1
     - echo y | android update sdk -u -a -t android-P
     - echo y | android update sdk -u -a -t extra-google-m2repository
     - echo y | android update sdk -u -a -t extra-android-m2repository