Moved sqlite3 override rules to db connection lib

- We have an already established location for special rules based on db client
- Removes the need to require config inside of overrides

core/server/data/db/connection.js

@@ -12,7 +12,12 @@ function configure(dbConfig) {
     const client = dbConfig.client;
 
     if (client === 'sqlite3') {
+        // Backwards compatibility with old knex behaviour
         dbConfig.useNullAsDefault = Object.prototype.hasOwnProperty.call(dbConfig, 'useNullAsDefault') ? dbConfig.useNullAsDefault : true;
+
+        // Force bthreads to use child_process backend until a worker_thread-compatible version of sqlite3 is published
+        // https://github.com/mapbox/node-sqlite3/issues/1386
+        process.env.BTHREADS_BACKEND = 'child_process';
     }
 
     if (client === 'mysql') {

core/server/overrides.js

@@ -1,5 +1,3 @@
-const config = require('../shared/config');
-
 /**
  * If we enable bluebird debug logs we see a huge memory usage.
  * You can reproduce by removing this line and import a big database export into Ghost.
@@ -7,15 +5,6 @@ const config = require('../shared/config');
  */
 process.env.BLUEBIRD_DEBUG = 0;
 
-/**
- * Force bthreads to use child_process backend until a worker_thread-compatible version of sqlite3 is published
- * https://github.com/mapbox/node-sqlite3/issues/1386
- */
-const isSQLite = config.get('database:client') === 'sqlite3';
-if (isSQLite) {
-    process.env.BTHREADS_BACKEND = 'child_process';
-}
-
 const moment = require('moment-timezone');
 
 /**