fix(integration): Don't mangle localforage internals (#5534)

Author: lforst

rollup/plugins/bundlePlugins.js

@@ -92,8 +92,16 @@ export function makeTerserPlugin() {
       properties: {
         // allow mangling of private field names...
         regex: /^_[^_]/,
-        // ...except for `_experiments`, which we want to remain usable from the outside
-        reserved: ['_experiments'],
+        reserved: [
+          // ...except for `_experiments`, which we want to remain usable from the outside
+          '_experiments',
+          // ...except for some localforage internals, which if we replaced them would break the localforage package
+          // with the error "Error: Custom driver not compliant": https://github.com/getsentry/sentry-javascript/issues/5527.
+          // Reference for which fields are affected: https://localforage.github.io/localForage/ (ctrl-f for "_")
+          '_driver',
+          '_initStorage',
+          '_support',
+        ],
       },
     },
     output: {