The Error message suggest a wrong NDK enviroment path, but both this enviroment var and the NDK Path in Unity point to the same location. Building worked in 2018.1 so far.
How to fix it for the time being is not to use Build And Run but just Build then you do adb install -r __.apk later manually. The APK will comes out just fine.
Thanks for the report. All the tests for burst were actually done with only “Build”. I was not aware about this difference. Will try to track this down.