Don't change working directory in the indexer (#558)

Summary:
This reverts a change that was added as part of
77681e9

I'm sure there must have been a reason for it, but it breaks running tests in parallel. In general nothing should be changing the working directory, because it's process-wide.

Pull Request resolved: #558

Reviewed By: phlalx

Differential Revision: D78210500

Pulled By: pepeiborra

fbshipit-source-id: f1bb25020dd28bba00ef78fa35574f265e3ad2fd

Author: simonmar

glean/lang/clang/Glean/Indexer/Cpp.hs

@@ -54,7 +54,6 @@ import Glean.LocalOrRemote ( BackendKind(..),
 import Glean.Util.Service
 import qualified Glean.Interprocess.Worklist as Worklist
 import qualified Glean.Handler as GleanHandler
-import System.Posix (changeWorkingDirectory)
 import Data.Aeson (decode, Object, Value (String))
 import Data.Foldable (toList)
 
@@ -230,11 +229,12 @@ indexerWith deriveToo = Indexer {
           forConcurrently_ [0 .. workers-1] $ \i -> bracket
             -- createProcess_ because we don't want the stdout/stderr handles
             -- to be closed
-            ( (if cdUp then pushd ".." else id) $
-              createProcess_
+            (createProcess_
                 "Cpp.index"
                 (proc clangIndex $ workerargs i)
-                  {std_out = stream, std_err = stream})
+                  {std_out = stream,
+                   std_err = stream,
+                   cwd = if cdUp then Just (takeDirectory currentDir) else Nothing})
             cleanupProcess
             $ \(_, _, _, ph) -> do
               ex <- waitForProcess ph
@@ -249,13 +249,6 @@ indexerWith deriveToo = Indexer {
     isPathPrefixOf :: FilePath -> FilePath -> Bool
     isPathPrefixOf prefix path = prefix == take (length prefix) path
 
-    pushd :: FilePath -> IO a -> IO a
-    pushd dir f = do
-      currentDir <- getCurrentDirectory
-      changeWorkingDirectory dir
-      res <- f
-      changeWorkingDirectory currentDir
-      pure res
 
     writeToDB backend repo = mapM_ $ \dataFile -> do
       dat <- BS.readFile dataFile