[infra] Translate _sources.gypi files to _sources.gni files

runtime/platform/platform_sources.gypi

Index: runtime/platform/platform_sources.gypi
diff --git a/runtime/platform/platform_sources.gypi b/runtime/platform/platform_sources.gypi
deleted file mode 100644
index 7327ad35e503892d9378a00c03394e69418f86fd..0000000000000000000000000000000000000000
--- a/runtime/platform/platform_sources.gypi
+++ /dev/null
@@ -1,15 +0,0 @@
-# Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
-# for details. All rights reserved. Use of this source code is governed by a
-# BSD-style license that can be found in the LICENSE file.
-
-# This file contains sources shared between the vm and bin components.
-{
-  'sources': [
-    'assert.cc',
-    'hashmap.cc',
-    'floating_point_win.cc',
-    'signal_blocker.h',
-    'text_buffer.cc',
-    'utils.cc',
-  ],
-}