Set executable bit on cert-maker.bat

NOTRY=true
TBR=cpu@chromium.org

Review URL: https://codereview.chromium.org/115333003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240705 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240705