[fuchsia] GN build support for Fuchsia OS and fuchsia_test target

runtime/vm/BUILD.gn

 # Copyright (c) 2014, 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.
 
 config("libdart_vm_config") {
-  libs = [
-    "dl",
-  ]
+  if (!is_fuchsia) {
+    libs = [ "dl" ]
 
-  if (!is_android) {
-    libs += [ "pthread" ]
+    if (!is_android) {
+      libs += [ "pthread" ]
 
-    if (is_linux) {
-      libs += [ "rt" ]
+      if (is_linux) {
+        libs += [ "rt" ]
+      }
     }
   }
 }
 
 
 static_library("libdart_platform") {
   configs += ["..:dart_config", "..:dart_product_config"]
   public_configs = [":libdart_vm_config"]
 
   platform_headers_gypi =
@@ skipping 206 matching lines @@
     ["developer", "developer", true, "../../sdk/lib/developer", "../lib"],
     ["_internal", "internal", true, "../../sdk/lib/internal", "../lib"],
     ["isolate", "isolate", true, "../../sdk/lib/isolate", "../lib"],
     ["math", "math", true, "../../sdk/lib/math", "../lib"],
     ["mirrors", "mirrors", true, "../../sdk/lib/mirrors", "../lib"],
     ["profiler", "profiler", false, "../../sdk/lib/profiler"],
     ["typed_data", "typed_data", false, "../lib"],
     ["_vmservice", "vmservice", true, "../../sdk/lib/vmservice", "../lib"],
   ]
 }