[gn] Forward the 'pool' parameter through dart actions

Related: https://github.com/flutter/flutter/issues/86946

Change-Id: Ie33c93a76d6107760655a7769c6541222e169c75
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/208060
Reviewed-by: Siva Annamalai <asiva@google.com>
Commit-Queue: Zach Anderson <zra@google.com>

utils/application_snapshot.gni

@@ -82,6 +82,9 @@ template("_application_snapshot") {
   # Build the kernel file using the prebuilt VM to speed up the debug and
   # simulator builds.
   prebuilt_dart_action(target_name + "_dill") {
+    if (defined(invoker.pool)) {
+      pool = invoker.pool
+    }
     deps = extra_deps + [
              "$_dart_root/runtime/vm:kernel_platform_files($host_toolchain)",
              "$_dart_root/runtime/vm:vm_platform",
@@ -131,6 +134,9 @@ template("_application_snapshot") {
 
   # Create a snapshot from kernel built above.
   dart_action(target_name) {
+    if (defined(invoker.pool)) {
+      pool = invoker.pool
+    }
     deps = extra_deps + [ ":${target_name}_dill" ]
     depfile = "$output.d"