Build fails on armv7

[seemethere]

Since moby/moby#38050 our nightly builds for Docker CE have been failing with:

Install rootlesskit version 3c4582e950e3a67795c2832179c125b258b78124
+ echo 'Install rootlesskit version 3c4582e950e3a67795c2832179c125b258b78124'
+ git clone https://github.com/rootless-containers/rootlesskit.git /tmp/tmp.YNt7AorSyx/src/github.com/rootless-containers/rootlesskit
Cloning into '/tmp/tmp.YNt7AorSyx/src/github.com/rootless-containers/rootlesskit'...
+ cd /tmp/tmp.YNt7AorSyx/src/github.com/rootless-containers/rootlesskit
+ git checkout -q 3c4582e950e3a67795c2832179c125b258b78124
+ go build -ldflags= -o /build//rootlesskit github.com/rootless-containers/rootlesskit/cmd/rootlesskit
# github.com/rootless-containers/rootlesskit/pkg/network/iputils
pkg/network/iputils/iputils.go:18:12: constant 4294967295 overflows int

This error only occurs when we're running on armv7 (arm32) machines.

CC @AkihiroSuda