I am getting this error after importing and trying to build the gdk-apidemo-sample-master in Android Studio:
Gradle sync failed: Cause: failed to find tar
Step by step solution, that works for me on the newest Android Studio 3.1.2:
classpath in the /build.gradle to new one (currently
classpath 'com.android.tools.build:gradle:3.1.2' works good).IDE will now correctly inform you about any other necessary updates. You can safely accept updating Gradle version, as it's working good now. At least in my project everything went flawlessly.
Examples of IDE prompts after above line change and opening the project:
Edit: As @Marcello Cuoghi said you might also need to select Launch: Nothing in the Run->Edit Configurations...->Launch Options.
Also in the app/build.gradle file change runProguard false to minifyEnabled true (usually not needed, but I had such once).