android-studio: set `ANDROID_EMULATOR_USE_SYSTEM_LIBS`

This change sets an environment variable to ensure that Android Studio
uses the correct drivers to avoid any breackage when trying to run a
native application on a virtual device.

Without proper configuration `android-studio` would be unable to load
the drivers for the AVD and yield messages like this:

```
3:32 PM	Executing tasks: [:app:assembleDebug]

3:32 PM	Emulator: libGL error: unable to load driver: i965_dri.so

3:32 PM	Emulator: libGL error: driver pointer missing

3:32 PM	Emulator: libGL error: failed to load driver: i965

3:32 PM	Emulator: libGL error: unable to load driver: i965_dri.so

3:32 PM	Emulator: libGL error: driver pointer missing

3:32 PM	Emulator: libGL error: failed to load driver: i965

3:32 PM	Emulator: libGL error: unable to load driver: swrast_dri.so

3:32 PM	Emulator: libGL error: failed to load driver: swrast

3:32 PM	Emulator: X Error of failed request:  BadValue (integer parameter out of range for operation)

3:32 PM	Emulator: Major opcode of failed request:  155 (GLX)

3:32 PM	Emulator: Minor opcode of failed request:  24 (X_GLXCreateNewContext)

3:32 PM	Emulator: Value in failed request:  0x0

3:32 PM	Emulator: Serial number of failed request:  64

3:32 PM	Emulator: Current serial number in output stream:  65

3:32 PM	Emulator: emulator: ERROR: Missing initial data partition file: /home/ma27/.android/avd/Nexus_5X_API_27.avd/userdata.img

3:32 PM	Emulator: Process finished with exit code 1

3:32 PM	Gradle build finished with 2 warnings(s) in 6s 378ms
```

For further reference have a look at the following StackOverflow
message: https://stackoverflow.com/a/40790339