Also ignore export-template.h when invoking tools/presubmit.py

R=machenbach@chromium.org
NOTRY=true
NOTREECHECKS=true

Bug: 
Change-Id: Ib6d3768a9e0cfb9ea5fdcece25325e8d498520af
Reviewed-on: https://chromium-review.googlesource.com/493288Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45028}

tools/presubmit.py

@@ -221,7 +221,7 @@ class CppLintProcessor(SourceFileProcessor):
     return (super(CppLintProcessor, self).IgnoreDir(name)
               or (name == 'third_party'))
 
-  IGNORE_LINT = ['flag-definitions.h']
+  IGNORE_LINT = ['export-template.h', 'flag-definitions.h']
 
   def IgnoreFile(self, name):
     return (super(CppLintProcessor, self).IgnoreFile(name)