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..bb64f59475762b25f18ecb024fece7d5aa62502f 100644
--- a/utils/generate_patch_sdk.gni
+++ b/utils/generate_patch_sdk.gni
@@ -28,7 +28,7 @@ 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" ]
     }
 
     script = "$_dart_root/tools/patch_sdk.py"
@@ -48,9 +48,9 @@ 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)",
-              "root_out_dir")
+      dart_out_dir =
+          get_label_info("$_dart_root/runtime/bin:dart_bootstrap_host_arch",
+                         "root_out_dir")
       dart_bootstrap = rebase_path(
               "$dart_out_dir/dart_bootstrap_host_arch$executable_suffix")
       args += [