Introduce dart_host_toolchain arg, remove '--checked' option from patch_sdk.py

utils/generate_patch_sdk.gni

Index: utils/generate_patch_sdk.gni
diff --git a/utils/generate_patch_sdk.gni b/utils/generate_patch_sdk.gni
index 4ec995784dd982469c7308f03bbbecee89a65228..3c05feb50b4adbe02043a555fb02eba59a22cc0a 100644
--- a/utils/generate_patch_sdk.gni
+++ b/utils/generate_patch_sdk.gni
@@ -3,6 +3,7 @@
 # BSD-style license that can be found in the LICENSE file.
 
 import("../build/prebuilt_dart_sdk.gni")
+import("../build/dart_host_toolchain.gni")
 
 _dart_root = get_path_info("..", "abspath")
 
@@ -28,7 +29,7 @@ template("generate_patched_sdk") {
     }
 
     if (!prebuilt_dart_exe_works) {
-      deps += [ "$_dart_root/runtime/bin:dart_bootstrap_host_arch($host_toolchain)" ]
+      deps += [ "$_dart_root/runtime/bin:dart_bootstrap_host_arch($dart_host_toolchain)" ]
     }
 
     script = "$_dart_root/tools/patch_sdk.py"
@@ -49,7 +50,7 @@ template("generate_patched_sdk") {
     args = [ "--quiet" ]
     if (!prebuilt_dart_exe_works) {
       dart_out_dir = get_label_info(
-              "$_dart_root/runtime/bin:dart_bootstrap_host_arch($host_toolchain)",
+              "$_dart_root/runtime/bin:dart_bootstrap_host_arch($dart_host_toolchain)",
               "root_out_dir")
       dart_bootstrap = rebase_path(
               "$dart_out_dir/dart_bootstrap_host_arch$executable_suffix")