Enable build minification

Summary: This shaves another ~6MB of the zipped build. Less than I would have thought, but I haven't looked at the alternative options so far at all.

Reviewed By: nikoant

Differential Revision: D21131772

fbshipit-source-id: 641515d6f36fdeeffa5be81d64c2c1043a9e4e34

desktop/pkg-lib/src/runBuild.ts

@@ -77,6 +77,13 @@ export default async function runBuild(
     transformer: {
       ...baseConfig.transformer,
       babelTransformerPath: require.resolve('flipper-babel-transformer'),
+      minifierPath: 'metro-minify-terser',
+      minifierConfig: {
+        // see: https://www.npmjs.com/package/terser
+        keep_fnames: true,
+        module: true,
+        warnings: true,
+      },
     },
     resolver: {
       ...baseConfig.resolver,
@@ -87,7 +94,7 @@ export default async function runBuild(
   });
   await Metro.runBuild(config, {
     dev,
-    minify: false,
+    minify: !dev,
     resetCache: !dev,
     sourceMap: true,
     entry,