databases/mysql57-client: Fix build with 10.x default compiler/linker
The upstream seems merged our local-patches but
added a -R flag to its c++ [actually ld] command.
The -R $DIR is like -rpath on 11.x and CURRENT bases but not on 10.x
We then use -rpath to make sure it works on all supported bases.

Reported by: John W. O'Brien <john@saltant.com>
Sponsored by: Netzkommune GmbH