Add a chrome_official_syzyasan_builder target.

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index bf9083b98606458a60a5e68b02ddc51b71cac202..0812d4cb880d21ed4d38a8fef9758904f6b0bb9e 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -150,6 +150,7 @@ if (is_win) {
     ]
   }
 
+  # TODO(sebmarchand): Remove this once we stop supporting Syzygy (M54+).
   group("All_syzygy") {
     if (is_syzyasan || syzygy_optimize) {
       deps = [
@@ -158,6 +159,15 @@ if (is_win) {
       ]
     }
   }
+
+  if (is_syzyasan) {
+    group("chrome_official_syzyasan_builder") {
+      deps = [
+        ":All_syzygy",
+        ":chrome_official_builder_no_unittests",
+      ]
+    }
+  }
 }
 
 if (is_chromeos) {