Avoid double builds

rollup.config.js

@@ -93,8 +93,15 @@ export default async function ({ watch }) {
       assetFileNames: staticPath,
       exports: 'named',
     },
+    watch: {
+      clearScreen: false,
       // Don't watch the ts files. Instead we watch the output from the ts compiler.
-    watch: { clearScreen: false, exclude: ['**/*.ts', '**/*.tsx'] },
+      exclude: ['**/*.ts', '**/*.tsx'],
+      // Sometimes TypeScript does its thing a little slowly, which causes
+      // Rollup to build twice on each change. This delay seems to fix it,
+      // although we may need to change this number over time.
+      buildDelay: 250,
+    },
     preserveModules: true,
     plugins: [
       { resolveFileUrl, resolveImportMeta },