[fuchsia] Prepare for setting the Dart target architecture appropriately in the host binaries.

runtime/bin/BUILD.gn

Index: runtime/bin/BUILD.gn
diff --git a/runtime/bin/BUILD.gn b/runtime/bin/BUILD.gn
index 8d56d3f7b34958db96b428548f2f13c5507b1ee8..a08cb9d25f492ca180df01bae6d7d020feeb118b 100644
--- a/runtime/bin/BUILD.gn
+++ b/runtime/bin/BUILD.gn
@@ -696,57 +696,72 @@ dart_executable("dart_precompiled_runtime") {
   ]
 }
 
-dart_executable("dart_bootstrap") {
-  extra_configs = [
-    "..:dart_precompiler_config",
-    "..:dart_no_snapshot_config",
-  ]
-  extra_deps = [
-    ":generate_builtin_cc_file",
-    ":generate_io_cc_file",
-    ":generate_io_patch_cc_file",
-    ":generate_html_cc_file",
-    ":generate_html_common_cc_file",
-    ":generate_js_cc_file",
-    ":generate_js_util_cc_file",
-    ":generate_blink_cc_file",
-    ":generate_indexed_db_cc_file",
-    ":generate_cached_patches_cc_file",
-    ":generate_web_gl_cc_file",
-    ":generate_metadata_cc_file",
-    ":generate_web_sql_cc_file",
-    ":generate_svg_cc_file",
-    ":generate_web_audio_cc_file",
-    "..:libdart_nosnapshot_with_precompiler",
-  ]
-  extra_defines = [ "NO_OBSERVATORY" ]
-  extra_sources = [
-    "builtin.cc",
-    "builtin.h",
-    "dfe.cc",
-    "dfe.h",
-    "loader.cc",
-    "loader.h",
-    "observatory_assets_empty.cc",
-    "snapshot_empty.cc",
+template("dart_bootstrap_template") {
+  invoker_extra_configs = []
+  if (defined(invoker.extra_configs)) {
+    invoker_extra_configs += invoker.extra_configs
+  }
+  dart_executable(target_name) {
+    extra_configs = [
+                      "..:dart_precompiler_config",
+                      "..:dart_no_snapshot_config",
+                    ] + invoker_extra_configs
+    extra_deps = [
+      ":generate_builtin_cc_file",
+      ":generate_io_cc_file",
+      ":generate_io_patch_cc_file",
+      ":generate_html_cc_file",
+      ":generate_html_common_cc_file",
+      ":generate_js_cc_file",
+      ":generate_js_util_cc_file",
+      ":generate_blink_cc_file",
+      ":generate_indexed_db_cc_file",
+      ":generate_cached_patches_cc_file",
+      ":generate_web_gl_cc_file",
+      ":generate_metadata_cc_file",
+      ":generate_web_sql_cc_file",
+      ":generate_svg_cc_file",
+      ":generate_web_audio_cc_file",
+      "..:libdart_nosnapshot_with_precompiler",
+    ]
+    extra_defines = [ "NO_OBSERVATORY" ]
+    extra_sources = [
+      "builtin.cc",
+      "builtin.h",
+      "dfe.cc",
+      "dfe.h",
+      "loader.cc",
+      "loader.h",
+      "observatory_assets_empty.cc",
+      "snapshot_empty.cc",
+
+      # Include generated source files.
+      "$target_gen_dir/builtin_gen.cc",
+      "$target_gen_dir/io_gen.cc",
+      "$target_gen_dir/io_patch_gen.cc",
+      "$target_gen_dir/html_gen.cc",
+      "$target_gen_dir/html_common_gen.cc",
+      "$target_gen_dir/js_gen.cc",
+      "$target_gen_dir/js_util_gen.cc",
+      "$target_gen_dir/blink_gen.cc",
+      "$target_gen_dir/indexed_db_gen.cc",
+      "$target_gen_dir/cached_patches_gen.cc",
+      "$target_gen_dir/web_gl_gen.cc",
+      "$target_gen_dir/metadata_gen.cc",
+      "$target_gen_dir/web_sql_gen.cc",
+      "$target_gen_dir/svg_gen.cc",
+      "$target_gen_dir/web_audio_gen.cc",
+    ]
+  }
+}
 
-    # Include generated source files.
-    "$target_gen_dir/builtin_gen.cc",
-    "$target_gen_dir/io_gen.cc",
-    "$target_gen_dir/io_patch_gen.cc",
-    "$target_gen_dir/html_gen.cc",
-    "$target_gen_dir/html_common_gen.cc",
-    "$target_gen_dir/js_gen.cc",
-    "$target_gen_dir/js_util_gen.cc",
-    "$target_gen_dir/blink_gen.cc",
-    "$target_gen_dir/indexed_db_gen.cc",
-    "$target_gen_dir/cached_patches_gen.cc",
-    "$target_gen_dir/web_gl_gen.cc",
-    "$target_gen_dir/metadata_gen.cc",
-    "$target_gen_dir/web_sql_gen.cc",
-    "$target_gen_dir/svg_gen.cc",
-    "$target_gen_dir/web_audio_gen.cc",
-  ]
+dart_bootstrap_template("dart_bootstrap") {
+  extra_configs = [ "..:dart_use_target_arch_config" ]
+}
+
+# TODO(rmacnak): Remove if Fuchsia adds a checked-in SDK.
+dart_bootstrap_template("dart_bootstrap_host_arch") {
+  extra_configs = []
 }
 
 if (is_fuchsia) {