From c7c2abbb8b426896dd91fd983ef3863a7cea4ed3 Mon Sep 17 00:00:00 2001
From: Wesley Wigham <t-weswig@microsoft.com>
Date: Tue, 14 Jun 2016 17:35:32 -0700
Subject: [PATCH] Add needsUpdate check to lib tasks

---
 Gulpfile.ts | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Gulpfile.ts b/Gulpfile.ts
index 8f72d5ffa47..ff90d6e6417 100644
--- a/Gulpfile.ts
+++ b/Gulpfile.ts
@@ -279,6 +279,9 @@ for (const i in libraryTargets) {
         return path.join(libraryDirectory, s);
     }));
     gulp.task(target, false, [], function() {
+        if (!needsUpdate(sources, target)) {
+            return gulp.src(target);
+        }
         return gulp.src(sources).pipe(concat(target, {newLine: ""})).pipe(gulp.dest("."));
     });
 }