I cannot tell from the logs why you have this issue, though this seems related to your android NDK.
Can you please check the following.
Are you sure your android NDK installation is clean & completed successfully? In case of any doubt, delete, then reinstall the NDK as explained in the guide (be sure to use r17c version of the NDK)
Completely delete your workspace out folder ( rm -rf /home/zovomat/Workspace/groundsdk/out) and proceed again with a build; this time, use the following command:
./build.sh -p groundsdk-android -t build-jni -j1
Note the -j1 parameter that will restrict the build to a single core, which will result in a more sensible log output for me to investigate.
Please post the complete output (including all input commands) to pastebin, so I can further analyze the issue.
Thanks for the answer, somehow deleting everything and restarting from scratch did the job, although I had already tried it multiple times in the last days
However, thank you again for the help