Use getAdbExe() to retrieve adb path.

This will prevent adb related issues such as `a problem occurred starting process 'command 'adb''` when the adb executable is not found in the path.

build.gradle

@@ -184,8 +184,8 @@ android.applicationVariants.all { variant ->
 
 task runApplication() {
   def result = exec {
-    executable = 'adb'
+    executable = android.getAdbExe().toString()
     ignoreExitValue true
     args = ['shell', 'monkey', '-p', getPackageName(), '-c', 'android.intent.category.LAUNCHER', '1']
   }
-}
+}