Add work-around to symlink.gni to avoid "not up-to-date" ninja errors

Ninja bug: ninja-build/ninja#1186

BUG=646165

Review-Url: https://codereview.chromium.org/2344243002
Cr-Commit-Position: refs/heads/master@{#419751}

Author: agrieve

build/symlink.gni

@@ -19,6 +19,7 @@ template("symlink") {
     ]
     script = "//build/symlink.py"
     args = [
+      "--update-target-mtimes",
       "-f",
       rebase_path(invoker.source, get_path_info(invoker.output, "dir")),
       rebase_path(invoker.output, root_build_dir),

build/symlink.py

@@ -24,6 +24,7 @@ def Main(argv):
   parser = optparse.OptionParser()
   parser.add_option('-f', '--force', action='store_true')
   parser.add_option('--touch')
+  parser.add_option('--update-target-mtimes', action='store_true')
 
   options, args = parser.parse_args(argv[1:])
   if len(args) < 2:
@@ -49,6 +50,10 @@ def Main(argv):
         os.symlink(s, t)
       else:
         raise
+    if options.update_target_mtimes:
+      # Work-around for ninja bug:
+      # https://github.com/ninja-build/ninja/issues/1186
+      os.utime(s, None)
 
 
   if options.touch: