mysqlcppconn: export sql_mysql_get_driver_instance on all platforms

It was only exported in an MSVC build before, which is a regression from
the gbuild conversion (c322d509).

Change-Id: I46783dc5fff5383bad8f8292c615ba8daa071cf9

mysqlcppconn/Library_mysqlcppconn.mk

@@ -26,15 +26,8 @@ $(eval $(call gb_Library_set_include,mysqlcppconn,\
 	-I$(call gb_UnpackedTarball_get_dir,mysqlcppconn)/cppconn \
 ))
 
-# HACK: generate import lib for msvc
-ifeq ($(COM),MSC)
-$(eval $(call gb_Library_add_ldflags,mysqlcppconn,\
-	/EXPORT:sql_mysql_get_driver_instance \
-))
-endif
-
 $(eval $(call gb_Library_add_defs,mysqlcppconn,\
-	-DCPPCONN_LIB_BUILD \
+	-Dmysqlcppconn_EXPORTS \
 	$(if $(filter WNT,$(OS)),\
 	-DCPPDBC_WIN32 \
 	-D_CRT_SECURE_NO_WARNINGS \