scarthgap: samba 4.19.8 meets configure break as libldb version is not found

[junzhuimx]

As samba is upgrade to 4.19.8, the depended libldb should also upgrade to v2.8.1.
Recently, do_configure failed as:
| Checking for system pyldb-util (>=2.8.1 <=2.8.999) : not found
| ERROR: System library pyldb-util of version 2.8.1 not found, and bundling disabled

[junzhuimx]

@kraj The issue has caused "samba" build break for 1 week on branch "scarthgap", and the commit 09f8ef2 should cherry-picked from branch master

[kraj]

@junzhuimx thanks for reporting, I think it needs to come to stable maintainer @akuster 's notice. It would be better if you can send a patch which is backported and tested on scarthgap. That will make his life easier too.

[akuster]

I just cherry-picked it. it should land shortly

[junzhuimx]

@kraj and @akuster
the PR #879 can be merged to fix this issue.