[Fuchsia] Prepend test image with magenta data

BUILD.gn

 # 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") {
   if (defined(is_fuchsia) && (is_fuchsia || is_fuchsia_host)) {
     # Fuchsia has run_vm_tests marked testonly.
     testonly = true
   }
@@ skipping 219 matching lines @@
 
     action("generate_dart_test_image") {
       testonly = true
       deps = [
         ":generate_dart_test_manifest",
         "runtime/bin:dart",
         "runtime/bin:process_test",
         "runtime/bin:run_vm_tests",
       ]
 
+      # Compute path to magenta bootdata.bin
+      if (current_cpu == "arm64") {
+        magenta_bootdata =
+            "//out/build-magenta/build-magenta-qemu-arm64/bootdata.bin"
+      } else if (current_cpu == "x64") {
+        magenta_bootdata =
+            "//out/build-magenta/build-magenta-pc-x86-64/bootdata.bin"
+      } else {
+        assert(false, "unable to determine path to magenta's bootdata.bin")
+      }
+
       input = "$target_gen_dir/dart_test_tree.manifest"
       inputs = [
+        magenta_bootdata,
         input,
       ]
 
       output = "$root_out_dir/dart_test_tree.bin"
       outputs = [
         output,
       ]
 
       script = "//packages/gn/make_bootfs.py"
       args = [
         "--manifest",
         rebase_path(input),
         "--output-file",
         rebase_path(output),
         "--build-id-map",
         rebase_path("$target_gen_dir/build_id_map"),
         "--compress",
+        "--pre-binaries",
+        rebase_path(magenta_bootdata),
       ]
     }
   }
 }