[Chromoting] Disable building 64bit chromoting.msi file.

A recent bug http://crbug.com/613001 has been reported by AJ, which is due to a
bad signing parameter we are using. It causes the 64 bit signed MSI file won't
be able to execute correctly in curtain mode.
Since we do not release 64bit msi, we should not spend time to build it.


Review-Url: https://codereview.chromium.org/2073943002
Cr-Commit-Position: refs/heads/master@{#401031}
2 files changed