Dart: Changes to support building for Android.

mojo/dart/embedder/test/BUILD.gn

Index: mojo/dart/embedder/test/BUILD.gn
diff --git a/mojo/dart/embedder/test/BUILD.gn b/mojo/dart/embedder/test/BUILD.gn
index 478935d7eaaa21e9a91203829f4c34982c194f75..0a510718b043860ca3bc6187a863554acad04433 100644
--- a/mojo/dart/embedder/test/BUILD.gn
+++ b/mojo/dart/embedder/test/BUILD.gn
@@ -7,7 +7,7 @@ import("//testing/test.gni")
 
 action("generate_test_snapshot_bin") {
   deps = [
-    "//dart/runtime/bin:gen_snapshot",
+    "//dart/runtime/bin:gen_snapshot($host_toolchain)",
   ]
   inputs = [
     "test_snapshot.dart",
@@ -36,12 +36,14 @@ action("generate_test_snapshot_bin") {
     output,
   ]
 
+  gen_snapshot_dir = get_label_info(
+      "//dart/runtime/bin:gen_snapshot($host_toolchain)", "root_out_dir")
   script = "//dart/runtime/tools/create_snapshot_bin.py"
   builtin_path = rebase_path("//mojo/dart/embedder/builtin.dart")
   bindings_path = rebase_path("//mojo/public/dart/bindings.dart")
   core_path = rebase_path("//mojo/public/dart/core.dart")
   args = [
-    "--executable", rebase_path("$root_out_dir/gen_snapshot"),
+    "--executable", rebase_path("$gen_snapshot_dir/gen_snapshot"),
     "--package_root", rebase_path("$root_gen_dir"),
     "--script", rebase_path("test_snapshot.dart"),
     "--output_bin", rebase_path(output, root_build_dir),