Add empty dart:platform library.

runtime/vm/vm.gypi

Index: runtime/vm/vm.gypi
diff --git a/runtime/vm/vm.gypi b/runtime/vm/vm.gypi
index 904eb1b8dfd3dde5099dc0955854d89cb41ca0df..a2e02e6c5a353097ebf71eb0709f01ab27addd20 100644
--- a/runtime/vm/vm.gypi
+++ b/runtime/vm/vm.gypi
@@ -24,6 +24,8 @@
     'isolate_cc_file': '<(gen_source_dir)/isolate_gen.cc',
     'isolate_patch_cc_file': '<(gen_source_dir)/isolate_patch_gen.cc',
     'json_cc_file': '<(gen_source_dir)/json_gen.cc',
+    'platform_cc_file': '<(gen_source_dir)/platform_gen.cc',
+    'platform_patch_cc_file': '<(gen_source_dir)/platform_patch_gen.cc',
     'typed_data_cc_file': '<(gen_source_dir)/typed_data_gen.cc',
     'typed_data_patch_cc_file': '<(gen_source_dir)/typed_data_patch_gen.cc',
     'utf_cc_file': '<(gen_source_dir)/utf_gen.cc',
@@ -111,6 +113,7 @@
         'generate_json_cc_file#host',
         'generate_mirrors_cc_file#host',
         'generate_mirrors_patch_cc_file#host',
+        'generate_platform_cc_file#host',
         'generate_typed_data_cc_file#host',
         'generate_typed_data_patch_cc_file#host',
         'generate_utf_cc_file#host',
@@ -122,6 +125,7 @@
         '../lib/isolate_sources.gypi',
         '../lib/math_sources.gypi',
         '../lib/mirrors_sources.gypi',
+        '../lib/platform_sources.gypi',
         '../lib/typed_data_sources.gypi',
       ],
       'sources': [
@@ -144,6 +148,8 @@
         '<(json_cc_file)',
         '<(mirrors_cc_file)',
         '<(mirrors_patch_cc_file)',
+        '<(platform_cc_file)',
+        '<(platform_patch_cc_file)',
         '<(typed_data_cc_file)',
         '<(typed_data_patch_cc_file)',
         '<(utf_cc_file)',
@@ -163,6 +169,7 @@
         '../lib/isolate_sources.gypi',
         '../lib/math_sources.gypi',
         '../lib/mirrors_sources.gypi',
+        '../lib/platform_sources.gypi',
         '../lib/typed_data_sources.gypi',
       ],
       'sources': [
@@ -845,6 +852,85 @@
       ]
     },
     {
+      'target_name': 'generate_platform_cc_file',
+      'type': 'none',
+      'toolsets':['host'],
+      'includes': [
+        '../../sdk/lib/platform/platform_sources.gypi',
+      ],
+      'sources/': [
+        # Exclude all .[cc|h] files.
+        # This is only here for reference. Excludes happen after
+        # variable expansion, so the script has to do its own
+        # exclude processing of the sources being passed.
+        ['exclude', '\\.cc|h$'],
+      ],
+      'actions': [
+        {
+          'action_name': 'generate_platform_cc',
+          'inputs': [
+            '../tools/gen_library_src_paths.py',
+            '<(libgen_in_cc_file)',
+            '<@(_sources)',
+          ],
+          'outputs': [
+            '<(platform_cc_file)',
+          ],
+          'action': [
+            'python',
+            'tools/gen_library_src_paths.py',
+            '--output', '<(platform_cc_file)',
+            '--input_cc', '<(libgen_in_cc_file)',
+            '--include', 'vm/bootstrap.h',
+            '--var_name', 'dart::Bootstrap::platform_source_paths_',
+            '--library_name', 'dart:platform',
+            '<@(_sources)',
+          ],
+          'message': 'Generating ''<(platform_cc_file)'' file.'
+        },
+      ]
+    },
+    {
+      'target_name': 'generate_platform_patch_cc_file',
+      'type': 'none',
+      'toolsets':['host'],
+      'includes': [
+        # Load the runtime implementation sources.
+        '../lib/platform_sources.gypi',
+      ],
+      'sources/': [
+        # Exclude all .[cc|h] files.
+        # This is only here for reference. Excludes happen after
+        # variable expansion, so the script has to do its own
+        # exclude processing of the sources being passed.
+        ['exclude', '\\.cc|h$'],
+      ],
+      'actions': [
+        {
+          'action_name': 'generate_platform_patch_cc',
+          'inputs': [
+            '../tools/gen_library_src_paths.py',
+            '<(libgen_in_cc_file)',
+            '<@(_sources)',
+          ],
+          'outputs': [
+            '<(platform_patch_cc_file)',
+          ],
+          'action': [
+            'python',
+            'tools/gen_library_src_paths.py',
+            '--output', '<(platform_patch_cc_file)',
+            '--input_cc', '<(libgen_in_cc_file)',
+            '--include', 'vm/bootstrap.h',
+            '--var_name', 'dart::Bootstrap::platform_patch_paths_',
+            '--library_name', 'dart:platform',
+            '<@(_sources)',
+          ],
+          'message': 'Generating ''<(platform_patch_cc_file)'' file.'
+        },
+      ]
+    },
+    {
       'target_name': 'generate_typed_data_cc_file',
       'type': 'none',
       'toolsets':['host'],