[clang] [llvm] [Support][Modules] Ensure parent directory exists in LockFileManager (PR #187372)

[Jan Svoboda via cfe-commits]

jansvoboda11 wrote:

This unconditionally tries to create a new directory, even if one already exists, which is an unnecessary overhead for the more common happy path. Could we move the directory creation into this block?

```c++
  if (std::error_code EC = sys::fs::createUniqueFile(
          UniqueLockFileName, UniqueLockFileID, UniqueLockFileName))
    // NOTE: Create the directory here if we failed with "does not exist" error.
    //       Create it and call `createUniqueFile()` again.
    return createStringError(EC, "failed to create unique file " +
                                     UniqueLockFileName);
```

https://github.com/llvm/llvm-project/pull/187372