Further shorten the lastchange string.

Even the 40-character hash causes problems when the pieces of the string before
it push the length to >64 characters. Truncating it is a temporary fix until
we discuss ways to accept strings longer than 64 chars.

R=cmp@chromium.org, scottmg@chromium.org
NOTRY=True
BUG=406783

Review URL: https://codereview.chromium.org/499133003

Cr-Commit-Position: refs/heads/master@{#291626}

build/util/lastchange.py

@@ -109,7 +109,9 @@ def FetchGitRevision(directory):
       hsh = output
   if not hsh:
     return None
-  return VersionInfo('git', hsh)
+  # TODO(agable): Figure out a way to use the full hash instead of just a
+  # 12-character short hash. See crbug.com/406783.
+  return VersionInfo('git', hsh[:12])
 
 
 def FetchGitSVNURLAndRevision(directory, svn_url_regex):