chore: parallel builds with Makefile (#3854)

* Revert "revert: Makefile buff-ification (#3700) (#3848)"

This reverts commit e490bdd531.

* fix: fix slim targets in makefile

* fix: don't clobber slim binaries, make sure they're in the correct location

site/webpack.common.ts

@@ -60,6 +60,7 @@ export const createCommonWebpackConfig = (options?: { skipTypecheck: boolean }):
     // REMARK: It's important to use [contenthash] here to invalidate caches.
     filename: "bundle.[contenthash].js",
     path: path.resolve(__dirname, "out"),
+    clean: false,
   },
 
   // modules specify how different modules are loaded

site/webpack.prod.ts

@@ -47,8 +47,11 @@ export const config: Configuration = {
   output: {
     ...commonWebpackConfig.output,
 
-    // regenerate the entire dist/ directory when producing production builds
-    clean: true,
+    // Regenerate the entire out/ directory (except GITKEEP and out/bin/) when
+    // producing production builds
+    clean: {
+      keep: /(GITKEEP|bin\/)/,
+    },
   },
 
   plugins: [