Add Alibaba Cloud Linux

See: https://www.alibabacloud.com/en/product/alibaba-cloud-linux-2

Here is an example of the user-agent:
    libdnf (Alibaba Cloud Linux 3; generic; Linux.x86_64)

Author: metalefty

src/opesys.c

@@ -79,6 +79,7 @@ static const char *const os[][2] = {
   {"macOS", "macOS"},
   {"Darwin", "Darwin"},
 
+  {"Alibaba Cloud Linux", "Linux"},
   {"AlmaLinux", "Linux"},
   {"Amazon Linux", "Linux"},
   {"CloudLinux", "Linux"},