Update upstream sqlite package to 2.6.0.

[simolus3]

The interesting changes to the build script are:

1. We now use SQLite 3.47.2 instead of 3.47.0.
2. The buildscripts now support compiling a variant using sqlite3mc for encryption instead of the regular SQLite sources. From some very limited testing those builds seem to be compatible with PowerSync. But I didn't change the release script to actually publish them, so this is not something that affects us right now.

[stevensJourney]

Looks good to me!