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

runtime/bin/BUILD.gn

Index: runtime/bin/BUILD.gn
diff --git a/runtime/bin/BUILD.gn b/runtime/bin/BUILD.gn
index bff1387bb54f433cbaa90227fa1be7f04818c298..0868b4a4a69304365288da21a27bc4d9b57b7a9e 100644
--- a/runtime/bin/BUILD.gn
+++ b/runtime/bin/BUILD.gn
@@ -5,7 +5,10 @@
 
 declare_args() {
   dart_io_support = false
-  dart_boringssl_path = "../../third_party/boringssl"
+
+  if (!is_fuchsia) {
+    dart_boringssl_path = "../../third_party/boringssl"
+  }
 }
 
 
@@ -207,6 +210,7 @@ static_library("libdart_nosnapshot_with_precompiler") {
   ]
 }
 
+if (!is_fuchsia) {
 
 executable("gen_snapshot") {
   configs += ["..:dart_config",
@@ -355,3 +359,22 @@ source_set("embedded_dart_io") {
     "//third_party"
   ]
 }
+}  # !is_fuchsia
+
+if (is_fuchsia) {
+  executable("fuchsia_test") {
+    sources = [
+      "fuchsia_test.cc",
+      "log_fuchsia.cc",
+    ]
+
+    include_dirs = [
+      "..",
+      "../include"
+    ]
+
+    deps = [
+        ":libdart_nosnapshot"
+    ]
+  }
+}