[Fuchsia] Prepend test image with magenta data

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index cb428a3ae5cf1d2809138b82af10d5088fb027f8..38fd398fb103a5561def62f091a2e351f6a2457e 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -237,8 +237,20 @@ if (defined(is_fuchsia) && is_fuchsia) {
         "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,
       ]
 
@@ -256,6 +268,8 @@ if (defined(is_fuchsia) && is_fuchsia) {
         "--build-id-map",
         rebase_path("$target_gen_dir/build_id_map"),
         "--compress",
+        "--pre-binaries",
+        rebase_path(magenta_bootdata),
       ]
     }
   }