GN: Don't depend on dart_bootstrap if there is a usable prebuilt sdk

build/executable_suffix.gni

Index: build/executable_suffix.gni
diff --git a/utils/analysis_server/BUILD.gn b/build/executable_suffix.gni
similarity index 57%
copy from utils/analysis_server/BUILD.gn
copy to build/executable_suffix.gni
index 032a086d71eea777e9d9e9a3d6e3fc7d1f5dd6e9..e2b0dd8fae2d7d092719ae242ea4576203114d51 100644
--- a/utils/analysis_server/BUILD.gn
+++ b/build/executable_suffix.gni
@@ -2,9 +2,8 @@
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
-import("../invoke_dart.gni")
-
-application_snapshot("analysis_server") {
-  main_dart = "../../pkg/analysis_server/bin/server.dart"
-  training_args = [ "--help" ]
+if (defined(is_win) && is_win) {
+  executable_suffix = ".exe"
+} else {
+  executable_suffix = ""
 }