Thanks for the pointers! I suspect MariaDB developers will not do any code changes. The patch to fix https://github.com/MariaDB/server/tree/10.11/include/my_rdtsc.h needs to come from somebody with easy access to armel/armhf/mipsel/mips64el to test the patch and the knowledge to argument why the code change is correct.
Anybody here willing to take a stab on it?