linux: In diff mode, print files with init function that calls 0 initializers.

clang writes two of these for some reason, and due to the script not
printing these it took me a while to figure out why clang has initializers
for two more files.

BUG=360311
NOTRY=true

Review URL: https://codereview.chromium.org/251873003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@266323 0039d316-1c4b-4281-b951-d872f2087c98

tools/linux/dump-static-initializers.py

@@ -214,7 +214,10 @@ def main():
           ref_output.append(ref)
 
     if opts.diffable:
-      print '\n'.join('# ' + qualified_filename + ' ' + r for r in ref_output)
+      if ref_output:
+        print '\n'.join('# ' + qualified_filename + ' ' + r for r in ref_output)
+      else:
+        print '# %s: (empty initializer list)' % qualified_filename
     else:
       print '%s (initializer offset 0x%x size 0x%x)' % (qualified_filename,
                                                         addr, size)