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

runtime/bin/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.
 
 
 declare_args() {
   dart_io_support = false
-  dart_boringssl_path = "../../third_party/boringssl"
+
+  if (!is_fuchsia) {
+    dart_boringssl_path = "../../third_party/boringssl"
+  }
 }
 
 
 resources_sources_gypi =
     exec_script("../../tools/gypi_to_gn.py",
                 [rebase_path("vmservice/vmservice_sources.gypi")],
                 "scope",
                 ["vmservice/vmservice_sources.gypi"])
 
 # Generate a resources.cc file for the service isolate without Observatory.
@@ skipping 181 matching lines @@
 
   include_dirs = [
     "..",
   ]
 
   defines = [
     "DART_SHARED_LIB",
   ]
 }
 
+if (!is_fuchsia) {
 
 executable("gen_snapshot") {
   configs += ["..:dart_config",
               "..:dart_product_config",
               "..:dart_precompiler_config"]
   deps = [
     ":gen_resources_cc",
     ":gen_snapshot_dart_io",
     ":generate_builtin_cc_file",
     ":generate_io_cc_file",
@@ skipping 128 matching lines @@
     "log_macos.cc",
     "log_win.cc",
     "log.h",
   ]
 
   include_dirs = [
     "..",
     "//third_party"
   ]
 }
+}  # !is_fuchsia
+
+if (is_fuchsia) {
+  executable("fuchsia_test") {
+    sources = [
+      "fuchsia_test.cc",
+      "log_fuchsia.cc",
+    ]
+
+    include_dirs = [
+      "..",
+      "../include"
+    ]
+
+    deps = [
+        ":libdart_nosnapshot"
+    ]
+  }
+}