Clean up logic, variables, etc. in the Makefile and related files.
Bump nimterop and sqlcipher in `vendor/` to latest versions.
In addition to tests on GitHub Actions, manually test all static/shared
combinations on Linux, macOS, and Windows. Also, for each combination check
locally that a separately compiled `sqlite3` cli *cannot* read
e.g. `test/build/my.db` even with `PRAGMA key = '[password]';`. Likewise, check
that a separately compiled `sqlcipher` cli *can* read a database if and only if
the correct password is used, e.g. `PRAGMA key = 'qwerty';` for
`test/build/my.db`.
96c9d37940