### Please describe the problem.

Trying to build git-annex on Windows by running "stack build" as instructed by https://git-annex.branchable.com/install/Windows/ currently fails with the following error:

[[!format sh """

[305 of 636] Compiling Annex.PidLock

Annex\PidLock.hs:70:9: error:
    * Couldn't match expected type `Annex a' with actual type `IO a'
    * In a stmt of a 'do' block: gonopidlock
      In the expression:
        do let p = f (proc cmd ps)
           let gonopidlock = withCreateProcess p a
           gonopidlock
      In an equation for `pidLockChildProcess':
          pidLockChildProcess cmd ps f a
            = do let p = ...
                 let gonopidlock = ...
                 gonopidlock
    * Relevant bindings include
        gonopidlock :: IO a (bound at Annex\PidLock.hs:47:13)
        a :: Maybe Handle
             -> Maybe Handle -> Maybe Handle -> ProcessHandle -> IO a
          (bound at Annex\PidLock.hs:45:30)
        pidLockChildProcess :: FilePath
                               -> [String]
                               -> (CreateProcess -> CreateProcess)
                               -> (Maybe Handle
                                   -> Maybe Handle -> Maybe Handle -> ProcessHandle -> IO a)
                               -> Annex a
          (bound at Annex\PidLock.hs:45:1)
   |
70 |         gonopidlock
   |         ^^^^^^^^^^^

"""]]

This happens when trying to build both the most recent commit (20c7e6c) and the most recent tag (8.20200908).

- stack version: 2.3.3
- Windows version: Windows 7 Enterprise, version 6.1

> [[fixed|done]] --[[Joey]]
