MDEV-12439: MariaRocks produces numerous (spurious?) valgrind failures

Step#1: RocksDB files require a special #define when they are compiled
with valgrind. Without that, valgrind fails with an 'unimplemented syscall'
error for fcntl call.

storage/rocksdb/CMakeLists.txt

@@ -19,6 +19,9 @@ IF(HAVE_SCHED_GETCPU)
   ADD_DEFINITIONS(-DHAVE_SCHED_GETCPU=1 -DROCKSDB_SCHED_GETCPU_PRESENT)
 ENDIF()
 
+IF(WITH_VALGRIND)
+  ADD_DEFINITIONS(-DROCKSDB_VALGRIND_RUN=1)
+ENDIF()
 
 # We've had our builders hang during the build process. This prevents MariaRocks
 # to be built on 32 bit intel OS kernels.