fix(bundling): use watch mode for rollup plugin (#26139)

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## Current Behavior
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`@nx/rollup/plugin` will not properly reload `rollup.config.js` files
when they are updated as they are cached.

## Expected Behavior
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`@nx/rollup/plugin` loads rollup configs with `watchMode` enabled so
that rollup utilizes the proper cache busting mechanism so that
`rollup.config.js` is properly reloaded.

## Related Issue(s)
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merged. -->

Fixes #

packages/rollup/src/plugins/plugin.ts

@@ -94,7 +94,9 @@ async function buildRollupTarget(
   const namedInputs = getNamedInputs(projectRoot, context);
   const rollupConfig = (
     (await loadConfigFile(
-      joinPathFragments(context.workspaceRoot, configFilePath)
+      joinPathFragments(context.workspaceRoot, configFilePath),
+      {},
+      true // Enable watch mode so that rollup properly reloads config files without reusing a cached version
     )) as { options: RollupOptions[] }
   ).options;
   const outputs = getOutputs(rollupConfig, projectRoot);