Disable more -Wmissing-profile warnings that are not
relevant when building PGO with GCC 9.

Remove storage/myisammrg/myrg_rsame.cc as it contains only dead code.

Avoid compiling sql/rpl_handler.cc and rpl_trx_tracking.cc twice.

Change-Id: I0a466607342aded8486c16d4a0e1deca94ee8b85