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

build/compiled_action.gni

Index: build/compiled_action.gni
diff --git a/build/compiled_action.gni b/build/compiled_action.gni
index e4e999ac576450eea1298443719c821e13369c63..228378dc8a9a7dd6f12359410a5ce9caa89e3464 100644
--- a/build/compiled_action.gni
+++ b/build/compiled_action.gni
@@ -66,6 +66,8 @@
 # saves unnecessarily compiling your tool for the target platform. But if you
 # need a target build of your tool as well, just leave off the if statement.
 
+import("dart_host_toolchain.gni")
+
 if (host_os == "win") {
   _host_executable_suffix = ".exe"
 } else {
@@ -97,7 +99,7 @@ template("compiled_action") {
     outputs = invoker.outputs
 
     # Constuct the host toolchain version of the tool.
-    host_tool = invoker.tool + "($host_toolchain)"
+    host_tool = invoker.tool + "($dart_host_toolchain)"
 
     # Get the path to the executable. Currently, this assumes that the tool
     # does not specify output_name so that the target name is the name to use.
@@ -150,7 +152,7 @@ template("compiled_action_foreach") {
     outputs = invoker.outputs
 
     # Constuct the host toolchain version of the tool.
-    host_tool = invoker.tool + "($host_toolchain)"
+    host_tool = invoker.tool + "($dart_host_toolchain)"
 
     # Get the path to the executable. Currently, this assumes that the tool
     # does not specify output_name so that the target name is the name to use.