The MariaDB 10.0.26 PowerPC build failure regression was identified and fixed in commit https://anonscm.debian.org/cgit/pkg-mysql/mariadb-10.0.git/commit/?id=de356c12d3ff73a20e65d1cd7756f3370208ccb2
This has been fixed also upstream and the new 10.0.27 should build OK on PowerPC. Now we just need to wait for somebody to publish a CVE regarding 10.0.27 so if qualitfies for security upload and this this issue can be closed...