Fix infinite loop in sky_tool listen if you didn’t specify —local-build

packages/flutter/lib/sky_tool

@@ -632,20 +632,19 @@ class StartListening(object):
             ]
             subprocess.check_call(cmd)
 
-            if not args.local_build:
+            if args.local_build:
                 # Currently sending to iOS only works if you are building Sky locally
                 # since we aren't shipping the sky_snapshot binary yet.
-                continue
 
-            # Build the snapshot
+                # Check if we can make a snapshot
+                sky_snapshot_path = None
                 if args.ios_sim_build_available:
                     sky_snapshot_path = os.path.join(args.sky_src_path, args.ios_sim_debug_build_path, 'clang_x64', 'sky_snapshot')
                 elif args.ios_build_available:
                     sky_snapshot_path = os.path.join(args.sky_src_path, args.ios_debug_build_path, 'clang_x64', 'sky_snapshot')
-            else:
-                # If there is no build available, we can't make a snapshot
-                continue
 
+                if sky_snapshot_path is not None:
+                    # If we can make a snapshot, do so and then send it to running iOS instances
                     cmd = [
                         sky_snapshot_path,
                         '--package-root=packages',