mariadb-connector-c: install my_config.h

https://github.com/bmwiedemann/openSUSE/blob/master/packages/m/mariadb-connector-c/mariadb-connector-c.spec#L152
https://github.com/NixOS/nixpkgs/issues/146340

arch, however, packages it in their mariadb-libs package which provides
connector-c so a nixpkgs mariadb maintainer may want to look into that
https://archlinux.org/packages/extra/x86_64/mariadb-libs/files/

pkgs/servers/sql/mariadb/connector-c/default.nix

@@ -52,6 +52,7 @@ stdenv.mkDerivation {
     ln -sv mariadb $dev/include/mysql
     ln -sv mariadb_version.h $dev/include/mariadb/mysql_version.h
     ln -sv libmariadb.pc $dev/lib/pkgconfig/mysqlclient.pc
+    install -Dm644 include/ma_config.h $dev/include/mariadb/my_config.h
   '';
 
   meta = {