don't always run LASTCHANGE

DEPS

 vars = {
   # Use this googlecode_url variable only if there is an internal mirror for it.
   # If you do not know, use the full path while defining your new deps entry.
   "googlecode_url": "http://%s.googlecode.com/svn",
   "sourceforge_url": "http://%(repo)s.svn.sourceforge.net/svnroot/%(repo)s",
   "webkit_trunk": "http://svn.webkit.org/repository/webkit/trunk",
   "nacl_trunk": "http://src.chromium.org/native_client/trunk",
   "webkit_revision": "106344",
   "chromium_git": "http://git.chromium.org/git",
   "swig_revision": "69281",
@@ skipping 467 matching lines @@
     # which takes ~20s, but clang speeds up builds by more than 20s.
     "pattern": ".",
     "action": ["python", "src/tools/clang/scripts/update.py", "--mac-only"],
   },
   {
     # Update the cygwin mount on Windows.
     "pattern": ".",
     "action": ["python", "src/build/win/setup_cygwin_mount.py", "--win-only"],
   },
   {
+    # Update LASTCHANGE.
+    "pattern": ".",
+    "action": ["python", "src/build/util/lastchange.py",
+               "-o", "src/build/util/LASTCHANGE"],
+  },
+  {
     # A change to a .gyp, .gypi, or to GYP itself should run the generator.
     "pattern": ".",
     "action": ["python", "src/build/gyp_chromium"],
   },
 ]