title: ANDROID_SDK_ROOT is undefined
body: <p>On my ubuntu 18.04 host machine
  I ran <code>sdkmanager</code>. After the update today
  the emulator does not work anymore.</p>
  
  <p>The error output:</p>
  
  <pre><code>sandbox@sanbox-host:~/.android$ emulator/./emulator -avd bykea1 -verbose
  emulator: Android emulator version 27.3.10.0 (build_id 4969155) (CL:751f3c993c814a52adf144c159615ce457c2d282)
  emulator: Found AVD name 'bykea1'
  emulator: Found AVD target architecture: x86_64
  emulator: argv[0]: 'emulator/./emulator'; program directory: '/home/sandbox/.android/emulator'
  emulator: Cannot find system image path. Please define ANDROID_SDK_ROOT
  emulator: Auto-config: -engine classic (based on configuration)
  PANIC: Cannot find AVD system path. Please define ANDROID_SDK_ROOT
  sandbox@sanbox-host:~/.android$ export ANDROID_SDK_ROOT=/home/sandbox/.android/
  sandbox@sanbox-host:~/.android$ emulator/./emulator -avd bykea1 -verbose
  emulator: Android emulator version 27.3.10.0 (build_id 4969155) (CL:751f3c993c814a52adf144c159615ce457c2d282)
  emulator: Found AVD name 'bykea1'
  emulator: Found AVD target architecture: x86_64
  emulator: argv[0]: 'emulator/./emulator'; program directory: '/home/sandbox/.android/emulator'
  emulator: Cannot find system image path. Please define ANDROID_SDK_ROOT
  emulator: Auto-config: -engine classic (based on configuration)
  PANIC: Broken AVD system path. Check your ANDROID_SDK_ROOT value [/home/sandbox/.android/]!
  </code></pre>