semaphore: Bad file descriptor errors

I generally set `semaphore: True` in my `cabal.project.local` to speed up my builds. Occasionally, I see `cabal build` fail with messages like this:
```
semWaitInterrruptible: invalid argument (Bad file descriptor)
cabal_semaphore_3: semUnlink: does not exist (No such file or directory)
```
I'm afraid I don't have a reliable reproducer to share, but I didn't see any other issues in the tracker mentioning semaphores and bad file descriptors, so I figured I'd file this anyway just in case.

**Expected behavior**
The build simply completes, but faster than with `semaphore: False`.

**System information**
- macOS 15.5
- `cabal`: 3.14.2.0
- `ghc`: 9.8.4

Start by exercising `cabal build` with `semaphore: True` in `cabal.project.local` on the reported macOS 15.5, Cabal 3.14.2.0, and GHC 9.8.4 setup. Investigate the `semWaitInterrruptible` and `semUnlink` failures; done means semaphore-enabled builds complete without these errors while retaining the expected speedup.

Written by the indexing model from the issue text.