Make list_files.py and list_dart_files.py return absolute paths for GN

runtime/vm/BUILD.gn

 # Copyright (c) 2014, 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.
 
 import("../../build/executable_suffix.gni")
 import("../../build/prebuilt_dart_sdk.gni")
 import("gypi_contents.gni")
 
 config("libdart_vm_config") {
   if (defined(is_fuchsia) && is_fuchsia) {
@@ skipping 393 matching lines @@
       deps = concatenation_target_names
       if (!prebuilt_dart_exe_works) {
         deps += [ "../bin:dart_bootstrap($host_toolchain)" ]
       }
 
       patches_dir = "$target_gen_dir/patches"
       patched_sdk_dir = "$root_out_dir/patched_sdk"
 
       script = "../../tools/patch_sdk.py"
 
-      # We list all files which make up the sdk (modulo patches) and get them back
-      # as a GN list object.
+      # We list all files which make up the sdk (modulo patches) and get them
+      # back as a GN list object.
       shared_sdk_sources = exec_script("../../tools/list_dart_files.py",
-                                       [ "../../sdk/lib" ],
+                                       [
+                                         "absolute",
+                                         rebase_path("../../sdk/lib"),
+                                       ],
                                        "list lines")
 
       # We list the `patch_sdk.dart` tool here because the [script] (which is
       # implicitly an input) will call it.
       inputs = [
         "../../tools/patch_sdk.dart",
       ]
 
-      # Files below are not patches, they will not be in [concatenation_files] but
-      # the `patch_sdk.dart` script will copy them into the patched sdk.
+      # Files below are not patches, they will not be in [concatenation_files]
+      # but the `patch_sdk.dart` script will copy them into the patched sdk.
       inputs += [
         "../lib/typed_data.dart",
         "../bin/builtin.dart",
         "../bin/vmservice/vmservice_io.dart",
         "../bin/vmservice/loader.dart",
         "../bin/vmservice/server.dart",
       ]
 
       # Add all the normal sdk sources.
       inputs += shared_sdk_sources
@@ skipping 84 matching lines @@
         "../lib",
       ],
       [
         "io",
         processed_gypis.bin_io_sources,
         "../bin",
       ],
     ]
   }
 }