GN build: Add process_test to precompiled runtime target.

BUILD.gn

 # Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 # 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.
 
 # This target will be built if no target is specified when invoking ninja.
 group("default") {
   if (defined(is_fuchsia) && (is_fuchsia || is_fuchsia_host)) {
     # Fuchsia has run_vm_tests marked testonly.
     testonly = true
   }
@@ skipping 31 matching lines @@
     "runtime/bin:sample_extension",
     "runtime/bin:test_extension",
     "runtime/vm:patched_sdk",
   ]
 }
 
 group("runtime_precompiled") {
   deps = [
     "runtime/bin:dart_bootstrap($host_toolchain)",
     "runtime/bin:dart_precompiled_runtime",
+    "runtime/bin:process_test",
     "runtime/vm:patched_sdk",
   ]
 }
 
 group("runtime_and_noopt") {
   if (defined(is_fuchsia) && (is_fuchsia || is_fuchsia_host)) {
     testonly = true
   }
   deps = [
     "runtime/bin:dart",
@@ skipping 111 matching lines @@
   deps = [
     ":create_sdk",
   ]
 }
 
 group("samples") {
   deps = [
     "runtime/bin:sample_extension",
   ]
 }