Minify DEV bundles with closure

The goal is to improve speed of the development by inlining and DCE unused
branches.

We have the ability to preserve some variable names and pretty print
in the production version so might as well do the same with DEV.

Author: sebmarkbage

scripts/rollup/build.js

@@ -361,7 +361,7 @@ function getPlugins(
     const isProduction = isProductionBundleType(bundleType);
     const isProfiling = isProfilingBundleType(bundleType);
 
-    const needsMinifiedByClosure = isProduction && bundleType !== ESM_PROD;
+    const needsMinifiedByClosure = bundleType !== ESM_PROD && bundleType !== ESM_DEV;
 
     return [
       // Keep dynamic imports as externals