Adds isolated install to HLS installs

app/ghcup/Main.hs

@@ -1718,7 +1718,14 @@ Report bugs at <https://gitlab.haskell.org/haskell/ghcup-hs/issues>|]
                           pure $ ExitFailure 4
 
           let installHLS InstallOptions{..} =
-                (case instBindist of
+                (case isolateDir of
+                  Just isoDir -> runInstTool instPlatform $ do
+                         (v, vi) <- liftE $ fromVersion instVer HLS
+                         let hlsVersion = (_tvVersion v)
+                         liftE $ installHLSBinIsolated isoDir hlsVersion
+                         pure vi
+                  Nothing ->
+                    case instBindist of
                        Nothing -> runInstTool instPlatform $ do
                          (v, vi) <- liftE $ fromVersion instVer HLS
                          liftE $ installHLSBin (_tvVersion v)

lib/GHCup.hs

@@ -667,6 +667,62 @@ installHLS' path inst ver = do
     (inst </> toF)
   lift $ chmod_755 (inst </> toF)
 
+-- | Installs hls binaries in an isolated location provided by user,
+-- doesn't make any symlinks
+
+installHLSBinIsolated :: ( MonadMask m
+                         , MonadCatch m
+                         , MonadReader env m
+                         , HasPlatformReq env
+                         , HasGHCupInfo env
+                         , HasDirs env
+                         , HasSettings env
+                         , MonadLogger m
+                         , MonadResource m
+                         , MonadIO m
+                         , MonadUnliftIO m
+                         , MonadFail m
+                         )
+                      => FilePath
+                      -> Version
+                      -> Excepts
+                           '[ AlreadyInstalled
+                            , CopyError
+                            , DigestError
+                            , DownloadFailed
+                            , NoDownload
+                            , NotInstalled
+                            , UnknownArchive
+                            , TarDirDoesNotExist
+#if !defined(TAR)
+                            , ArchiveResult
+#endif
+                            ]
+                           m
+                           ()
+installHLSBinIsolated isoDir ver = do
+  dlinfo <- liftE $ getDownloadInfo HLS ver
+
+  lift $ $(logDebug) [i|Requested to install hls version #{ver}|]
+
+  PlatformRequest {_rPlatform} <- lift getPlatformReq
+
+  -- download (or use cached version)
+  dl <- liftE $ downloadCached dlinfo Nothing
+
+  -- unpack
+  tmpUnpack <- lift withGHCupTmpDir
+  liftE $ unpackToDir tmpUnpack dl
+  void $ lift $ darwinNotarization _rPlatform tmpUnpack
+
+  -- the subdir of the archive where we do the work
+  workdir <- maybe (pure tmpUnpack) (liftE . intoSubdir tmpUnpack) (view dlSubdir dlinfo)
+
+  lift $ $(logInfo) [i|isolated installing HLS to #{isoDir}|]
+
+  liftE $ installHLS' workdir isoDir ver
+
+
 -- | Installs hls binaries @haskell-language-server-\<ghcver\>@
 -- into @~\/.ghcup\/bin/@, as well as @haskell-languager-server-wrapper@.
 installHLSBin :: ( MonadMask m