If you, like me, love keeping your software up-to-date, chances are you have faced with this error message when you tried to build and run your Unity project on Android.
This happens because Unity (and as far I can see, although cannot personally validate Eclipse as well) used to rely on a build process that got deprecated with the release 25.2.3 of Android SDK Build Tools.
Hopefully, Unity will catch-up, but in the meanwhile, the only way to workaround this issue is by downgrading the build tools to version 25.2.2 or lower. Here is how to do this. First, download the build tools using one of the links below:
Then we need to extract the zip directory and replace the content inside of your installation of the Android SDK.
For the reference, by deafult, Android SDK is installed in the following directories:
Mac OS X: