lastchange: skip over git-svn "rebuilding..." lines

Sometimes git-svn prints extra status info.
From a glance at the source, there's no flag to skip it.
So just skip it when parsing.

Review URL: http://codereview.chromium.org/6349010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@72360 0039d316-1c4b-4281-b951-d872f2087c98

build/util/lastchange.py

@@ -63,7 +63,9 @@ def FetchSVNRevision(command, directory):
   attrs = {}
   for line in proc.stdout:
     line = line.strip()
-    if not line:
+    # git-svn can print out extra "Rebuilding ..." lines, which we don't
+    # care about and want to skip over.
+    if not line or ': ' not in line:
       continue
     key, val = line.split(': ', 1)
     attrs[key] = val