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

build/symlink.py

Index: build/symlink.py
diff --git a/build/symlink.py b/build/symlink.py
index 5a261dcad93e1bddc77b42312f552a12dc8c131f..53bbfd371c362b578d91b97db7c6ba77fc8021f0 100755
--- a/build/symlink.py
+++ b/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 +50,14 @@ 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
+      try:
+        os.utime(s, None)
+      except:
+        # This can fail if the target doesn't exist.
+        pass
 
 
   if options.touch: