Extension needs to be valid

Author: mpilgrem

src/Stack/Build/Execute.hs

@@ -1934,7 +1934,8 @@ singleTest topts testsToRun ac ee task installedMap = do
                     fp' = eeTempDir ee </> testGhcEnvRelFile
                 -- Add a random suffix to avoid conflicts between parallel jobs
                 -- See https://github.com/commercialhaskell/stack/issues/5024
-                randomSuffix <- ("-"<>) . show <$> liftIO (randomIO :: IO Int)
+                randomInt <- liftIO (randomIO :: IO Int)
+                let randomSuffix = "." <> (show $ abs randomInt)
                 fp <- toFilePath <$> addExtension randomSuffix fp'
                 let snapDBPath = toFilePathNoTrailingSep (bcoSnapDB $ eeBaseConfigOpts ee)
                     localDBPath = toFilePathNoTrailingSep (bcoLocalDB $ eeBaseConfigOpts ee)