Cannot compile examples for Android with Qt 5.13.0 beta2

When trying to build any example with Qt 5.13.0 beta2 Android binaries (x86, arm64, armv7), the build fails with:

['Project ERROR: You need to set the ANDROID_NDK_ROOT environment variable to point to your Android NDK.', 'Could not read qmake configuration file /home/qt/RTA/qt5/5.13.0/android_x86/mkspecs/android-clang/qmake.conf.', 'Error processing project file: /home/qt/RTA/qt5/Examples/Qt-5.13.0/quickcontrols2/contactlist/contactlist.pro', 'make: *** No targets specified and no makefile found.  Stop.', ''] 

Asked from the CI-team if something has changed in Android env, and they said that the ndk was updated from ndk-r19b to ndk-r19c (on Linux) in between the making of the binaries and the RTA tests. The same machines are used to create and test the packages.

Does not affect Windows or macOS.