Partially revert "🏗 Parallelize dist steps (#35943)" (#36176)

* Revert "🏗 Parallelize `dist` steps (#35943)"

This reverts commit 1e2c808.

* Partially allow parallelization for smaller tasks

* Also include `compileAllJs` in the parallelized part

build-system/tasks/dist.js

@@ -114,19 +114,20 @@ async function dist() {
   await runPreDistSteps(options);
 
   // These steps use closure compiler. Small ones before large (parallel) ones.
-  const steps = [];
   if (argv.core_runtime_only) {
-    steps.push(compileCoreRuntime(options));
+    await compileCoreRuntime(options);
   } else {
-    steps.push(buildExperiments());
-    steps.push(buildLoginDone('0.1'));
-    steps.push(buildWebPushPublisherFiles());
-    steps.push(buildCompiler());
-    steps.push(compileAllJs(options));
+    await Promise.all([
+      buildExperiments(),
+      buildLoginDone('0.1'),
+      buildWebPushPublisherFiles(),
+      buildCompiler(),
+      compileAllJs(options),
+    ]);
   }
 
   // This step internally parses the various extension* flags.
-  steps.push(buildExtensions(options));
+  await buildExtensions(options);
 
   // This step is to be run only during a full `amp dist`.
   if (
@@ -135,11 +136,9 @@ async function dist() {
     !argv.extensions_from &&
     !argv.noextensions
   ) {
-    steps.push(buildVendorConfigs(options));
+    await buildVendorConfigs(options);
   }
 
-  await Promise.all(steps);
-
   // This step is required no matter which binaries are built.
   await formatExtractedMessages();