Make test-ghc-env files unique across parallel jobs

Since the build temporary directory is shared between jobs, we can't use
the same file name for the `test-ghc-env` for all of them.

Fixes commercialhaskell#5024

package.yaml

@@ -104,6 +104,7 @@ dependencies:
 - primitive
 - process
 - project-template
+- random
 - retry
 - rio >= 0.1.21.0
 - rio-prettyprint >= 0.1.1.0

src/Stack/Build/Execute.hs

@@ -93,6 +93,7 @@ import           System.PosixCompat.Files (createLink, modificationTime, getFile
 import           RIO.PrettyPrint
 import           RIO.Process
 import           Pantry.Internal.Companion
+import           System.Random (randomIO)
 
 -- | Has an executable been built or not?
 data ExecutableBuildStatus
@@ -1918,10 +1919,11 @@ singleTest topts testsToRun ac ee task installedMap = do
                 -- see e.g. https://github.com/doctest/issues/119
                 -- also we set HASKELL_DIST_DIR to a package dist directory so
                 -- doctest will be able to load modules autogenerated by Cabal
+                ghcEnvRandomId <- liftIO (randomIO :: IO Int)
                 let setEnv f pc = modifyEnvVars pc $ \envVars ->
                       Map.insert "HASKELL_DIST_DIR" (T.pack $ toFilePath buildDir) $
                       Map.insert "GHC_ENVIRONMENT" (T.pack f) envVars
-                    fp = toFilePath $ eeTempDir ee </> testGhcEnvRelFile
+                    fp = toFilePath (eeTempDir ee </> testGhcEnvRelFile) <> show ghcEnvRandomId
                     snapDBPath = toFilePathNoTrailingSep (bcoSnapDB $ eeBaseConfigOpts ee)
                     localDBPath = toFilePathNoTrailingSep (bcoLocalDB $ eeBaseConfigOpts ee)
                     ghcEnv =

stack.cabal

@@ -282,6 +282,7 @@ library
     , primitive
     , process
     , project-template
+    , random
     , retry
     , rio >=0.1.21.0
     , rio-prettyprint >=0.1.1.0
@@ -405,6 +406,7 @@ executable stack
     , primitive
     , process
     , project-template
+    , random
     , retry
     , rio >=0.1.21.0
     , rio-prettyprint >=0.1.1.0
@@ -527,6 +529,7 @@ executable stack-integration-test
     , primitive
     , process
     , project-template
+    , random
     , retry
     , rio >=0.1.21.0
     , rio-prettyprint >=0.1.1.0
@@ -654,6 +657,7 @@ test-suite stack-test
     , primitive
     , process
     , project-template
+    , random
     , raw-strings-qq
     , retry
     , rio >=0.1.21.0