Address new analyzer warnings

[joeloff]

Changes in the runtime, dotnet/runtime#54147, are causing analyzer errors. To unblock the dependency flow, we suppressed the new failures.

This bug is intended to track fixing them in the SDK.

Original PR where the analyzer failures showed up: #18292

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[danmoseley]

Recording context here -- this means that the CLI builds when targeting non Windows are apparently using API that only work on Windows.