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Issue Description
I have added Swift Package ("nio" branch) with Xcode 11 intergated SPM. Once I do "archive" with selected iOS-platform, the build fails with "arithmetic operations overflow" in GRPCTimeoutUnit.
I suppose this is 32-bit related issue because by default Xcode adds armv7 architecture to the build.
I'm on 10.15, but I get same results on 10.14.
Archive is ok for macOS builds (i386/x86_64)

Environment
| Key |
Value |
| OS Version |
10.15 |
| Swift Version |
5.1 |
| Xcode Version |
11.0 beta (11M336w) |