prevent rollup from adding [Symbol.toStringTag]: 'Module' to CJS files

rollup/npmHelpers.js

@@ -44,8 +44,14 @@ export function makeBaseNPMConfig(options = {}) {
       // output individual files rather than one big bundle
       preserveModules: true,
 
-      // any wrappers or helper functions generated by rollup can use ES6 features
-      generatedCode: 'es2015',
+      // Allow wrappers or helper functions generated by rollup to use any ES6 features except symbols. (Symbols in
+      // general are fine, but the `[Symbol.toStringTag]: 'Module'` which Rollup adds alongside `__esModule:
+      // true` in CJS modules makes it so that Jest <= 29.2.2 crashes when trying to mock generated `@sentry/xxx`
+      // packages. See XXXXX.)
+      generatedCode: {
+        preset: 'es2015',
+        symbols: false,
+      },
 
       // don't add `"use strict"` to the top of cjs files
       strict: false,