Under Windows and Packages CI workflows the previous approach to testing
that an existing spellings DB file is reused didn't work since it relied
on an auxiliary test ensuring that a spellings database cannot be
created in a read-only directory, whereas
1. under Windows a temporary directory couldn't be made read-only
(leading to the failure of the auxiliary test)
2. in the Packages workflow the build was run with root privileges
and the read-onliness of the target directory was ignored
(leading to the same failure).
So the test was rewritten to actually check the content of the target
directory as well as the modifications times of the target directory and
the database file.
Packages workflow jobs run under Ubuntu 22.04 Jammy and 24.04 Noble with
different versions of libxapian.so. So the spelling correction unit test
must adapt accordingly.
The path parameter of the SpellingsDB constructor has been changed to
denote the path of the cache directory where spellings databases for
different ZIM archive should be stored. The filename of the spellings
database is generated from the ZIM archive UUID and the current version
of the spellings database implementation.
