[cs] add sqlite drivers to cs-unsafe as well

tests/unit/compile-cs-unsafe.hxml

@@ -8,3 +8,6 @@ compile-each.hxml
 -D unsafe
 -cs bin/cs_unsafe
 -net-lib native_cs/bin/native_cs.dll
+-net-lib cs_drivers/System.Data.dll
+-net-lib cs_drivers/System.Xml.dll
+-net-lib cs_drivers/Mono.Data.Sqlite.dll