Document macOS PKG installer createdump executable bit regression (#10149)

* Initial plan

* Add known issue for macOS createdump missing executable bit

Co-authored-by: hoyosjs <19413848+hoyosjs@users.noreply.github.com>

* Apply suggestion from @hoyosjs

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: hoyosjs <19413848+hoyosjs@users.noreply.github.com>

Author: Copilot

release-notes/10.0/known-issues.md

@@ -80,3 +80,12 @@ See [the GitHub issue](https://github.com/dotnet/runtime/issues/121193) for more
 ### Available Workarounds
 
 Using a concrete `T[]` array instead of `IEnumerable<T>` for the configuration property works around this issue.
+
+## macOS PKG installers missing executable bit on `createdump`
+
+SDK and runtime installers for macOS install a `createdump` binary that lacks the executable bit. This means that scenarios that request a dump (test hang collector, `dotnet-dump collect`, collecting dumps on crash through environment variable, etc.) will fail with an error indicating that `createdump` cannot be executed.
+
+### Available Workaround for createdump
+
+- Add the executable bit to `shared/Microsoft.NETCore.App/10.0.0/createdump` manually using `chmod +x`
+- Use another runtime hosting mechanism (self-contained app, use a tarball installation of the runtime/SDK)