Include also ARM build of protoc in nuget package

[FooRider]

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[google-cla]

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[acozzette]

@FooRider Thank you for this pull request. We can't review it until you sign the CLA, but please let me know if you have any trouble doing that.

[FooRider]

@FooRider Thank you for this pull request. We can't review it until you sign the CLA, but please let me know if you have any trouble doing that.

Thanks, I had no problems with CLA, just not enough time to get through it at the time. CLA is now signed, hopefully the PR will pass.