Fix tracker build for COLLECT_API_ENDPOINT.

rollup.tracker.config.js

@@ -1,3 +1,4 @@
+import 'dotenv/config';
 import buble from '@rollup/plugin-buble';
 import replace from '@rollup/plugin-replace';
 import { terser } from 'rollup-plugin-terser';
@@ -12,6 +13,7 @@ export default {
     replace({
       '/api/collect': process.env.COLLECT_API_ENDPOINT || '/api/collect',
       delimiters: ['', ''],
+      preventAssignment: true,
     }),
     buble({ objectAssign: true }),
     terser({ compress: { evaluate: false } }),