MDEV-16605 Always include buf_madvise_do_dump in binaries

The "used" attribute seems to do this

ref: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#Common-Function-Attributes

storage/innobase/buf/buf0buf.cc

@@ -1182,6 +1182,7 @@ in the event that you want all of the memory to be dumped
 to a core file.
 
 Returns number of errors found in madvise calls. */
+MY_ATTRIBUTE((used))
 int
 buf_madvise_do_dump()
 {