Build: Failed to acquire dotnetup — SHA-512 checksum mismatch downloading dotnetup during InitializeToolset

## Build Information
Build: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1490592 (Attempt #1)
Leg Name: `AoT: macOS (arm64)` — 🟣 Build (InitializeToolset), also affects other legs
Pull request: dotnet/sdk#55109

## Error Details
During toolset initialization the build downloads the `dotnetup` daily binary from `https://aka.ms/dotnet/dotnetup/daily/...` and verifies its SHA-512 checksum. The download intermittently fails checksum verification, which aborts `InitializeToolset` and fails the whole `Build` step before anything is compiled. This forced a manual retry on PR dotnet/sdk#55109 (build `1490592` failed, later builds passed).

```
Installing SDK(s) '11.0.100-preview.5.26227.104' to '/Users/runner/work/1/s/.dotnet' via dotnetup...
Detected runtime: osx-arm64
Downloading https://aka.ms/dotnet/dotnetup/daily/dotnetup-osx-arm64
Verifying SHA-512 checksum...
Checksum mismatch.
Expected: c62ce30956eb521c65d5931cdc71c2d97a5fc0a42b11ca03bd7a6bdfcc93f56b5acd342afdac798d3eaed3473a960eb398c3e63bc8d957ba67a8278833b7883f
Actual: 95c124b189ecce81c9897afec8ce5125f54e75f999b487a994e078ff92cce64a6723462b449746933abee879106ab3754f443b7282a4fc46aa197edbc89c19f7
##[error](NETCORE_ENGINEERING_TELEMETRY=InitializeToolset) Failed to acquire dotnetup.
##[error]Bash exited with code '1'.
```

### Known Issue Error Message

**DO NOT USE JSON BELOW IF THIS IS A BUILD BREAK** otherwise build analysis will allow pull requests to merge that break the build worse. For a build break, do not use this issue form. Make a regular new issue.

Fill the error message using [step by step known issues guidance](https://github.com/dotnet/arcade/blob/main/Documentation/Build%20Analysis/KnownIssueJsonStepByStep.md).

```json
{
"ErrorMessage": "",
"ErrorPattern": "",
"BuildRetry": false,
"ExcludeConsoleLog": false
}
```