Issue 50737 - Allow building with rust online without vendoring
Bug Description:
Building --rust-enable without --rust-enable-offline still requires
predownloading the libraries.
Fix Description:
Setup .cargo/config on ./configure time allowing to subsequently do make
that would in a case automatically download necessary libraries (in
online mode).
Fixes https://pagure.io/389-ds-base/issue/50737
Author: Matus Honek <mhonek@redhat.com>
Review by: ???