Beginning work on GN build

BUILD.gn

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+# Copyright (c) 2016, 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 target will be built if no target is specified when invoking ninja.
+group("default") {
+  testonly = true
+  deps = [
+    "//runtime/bin:dart",
+  ]
+}
+
+    # {
+    #   # This is the target that is built on the VM build bots.  It
+    #   # must depend on anything that is required by the VM test
+    #   # suites.
+    #   'target_name': 'runtime',
+    #   'type': 'none',
+    #   'dependencies': [
+    #     'runtime/dart-runtime.gyp:dart',
+    #     'runtime/dart-runtime.gyp:dart_bootstrap#host',
+    #     'runtime/dart-runtime.gyp:run_vm_tests',
+    #     'runtime/dart-runtime.gyp:process_test',
+    #     'packages',
+    #     'runtime/dart-runtime.gyp:test_extension',
+    #     'runtime/dart-runtime.gyp:sample_extension',
+    #   ],
+    # },
+
+group("runtime") {
+  testonly = true
+  deps = [
+    "//runtime/bin:dart",
+    "//runtime/bin:dart_bootstrap($host_toolchain)",
+    "//runtime/bin:run_vm_tests",
+    "//runtime/bin:process_test",
+    "//pkg",
+  ]
+}