Automatic merge from submit-queue (batch tested with PRs 51047, 48573, 50764, 51092, 50578)
Use `select` to disable building static binaries if `--cpu=darwin`.
This change allows kubectl to be built on MacOS machines using
`bazel build //cmd/kubectl`.
Mac OS X doesn't support static binaries because it does not have a
stable syscall API. Userspace binaries are expected to dynamically
link against libcrt instead.
https://developer.apple.com/library/content/qa/qa1118/_index.html
```release-note
None
```
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