[Flaky Test] Microsoft.Build.Engine.UnitTests.NetTaskHost_E2E_Tests.NetTaskHost_SymlinkedSdkPath_ShouldNotCauseMSB4216

**Flaky-test key** (automated de-duplication — do not edit):
```text
flaky-test-id: Microsoft.Build.Engine.UnitTests.NetTaskHost_E2E_Tests.NetTaskHost_SymlinkedSdkPath_ShouldNotCauseMSB4216
```

## Evidence

- **Distinct sources:** 4 (4 distinct approved PRs)
- **Affected PRs:** #14318, #14352, #14354, #14371
- **Rolling build IDs:** (none in window)
- **Total failures:** 7
- **Legs:** CoreOnLinux, CoreOnMac
- **TFMs:** net10.0
- **Assembly:** Microsoft.Build.Engine.UnitTests
- **First seen:** 2026-07-13 | **Last seen:** 2026-07-15
- **Distinct error hashes:** 7 (sporadic, non-deterministic failure signatures)
- **Sample build:** [1506605](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1506605)

## Sample error

```
System.TimeoutException : Test failed due to timeout: process 76618 is active for more than 30 sec.
```

## Fully-qualified test name

`Microsoft.Build.Engine.UnitTests.NetTaskHost_E2E_Tests.NetTaskHost_SymlinkedSdkPath_ShouldNotCauseMSB4216`
Assembly: `Microsoft.Build.Engine.UnitTests`
Project: `src/Build.UnitTests/`

## Action

This test will be **quarantined** via `[ActiveIssue("https://github.com/dotnet/msbuild/issues/")]` (from `Microsoft.DotNet.XUnitV3Extensions`, namespace `Xunit`) until the underlying nondeterminism is fixed. The quarantine pipeline (def 344) will continue collecting signal over time.

> [!WARNING]
>
> Firewall blocked 1 domain
>
> The following domain was blocked by the firewall during workflow execution:
>
> - `awmgmcpg`
>> To allow these domains, add them to the `network.allowed` list in your workflow frontmatter:
>
> ```yaml
> network:
> allowed:
> - defaults
> - "awmgmcpg"
> ```
>
> See [Network Configuration](https://github.github.com/gh-aw/reference/network/) for more information.
>
>

> Generated by [Flaky Test Triage](https://github.com/dotnet/msbuild/actions/runs/29493043688) · 78.5 AIC · ⌖ 6.94 AIC · ⊞ 13.5K · [◷](https://github.com/search?q=repo%3Adotnet%2Fmsbuild+is%3Aissue+%22gh-aw-workflow-call-id%3A+dotnet%2Fmsbuild%2Fflaky-test-detector.agent%22&type=issues)

Start with the fully qualified NetTaskHost_SymlinkedSdkPath_ShouldNotCauseMSB4216 test in src/Build.UnitTests/ and review the sample build failure. Compare its CoreOnLinux and CoreOnMac behavior, focusing on the 30-second process timeout and the seven differing error signatures. Done means the test is reliable across the affected legs and no longer needs quarantine.

Written by the indexing model from the issue text.