CI: Split build and connectedCheck tasks

Advantages:

* Failing unit tests don't keep the android tests from running
* CI should be overall faster as the tasks get run in parallel and the
  former `gradle` task was the longest by far

This will later simplify the multiplexing of the android tests onto
multiple emulators.

.gitlab-ci.yml

@@ -10,7 +10,7 @@ variables:
   # switch glibc to a memory conserving mode
   MALLOC_ARENA_MAX: "2"
 
-gradle:
+build:
   script:
     - export GRADLE_USER_HOME=$PWD/.gradle
     # always report on lint errors to the build log
@@ -23,6 +23,10 @@ gradle:
           done;
           exit 1;
       }
+
+connectedCheck:
+  script:
+    - export GRADLE_USER_HOME=$PWD/.gradle
     - emulator64-arm -avd fcl-test-$AVD_SDK -no-skin -no-audio -no-window &
     - ./tools/wait-for-emulator
     - adb shell input keyevent 82 &