Fix build

Author: uhbif19

haskell-language-server.cabal

@@ -279,7 +279,7 @@ common hlint
     cpp-options: -Dhlint
 
 common stan
-  if flag(stan) && impl(ghc < 9.0)
+  if flag(stan) && (impl(ghc > 8.6) && impl(ghc < 9.0))
     build-depends: hls-stan-plugin ^>= 1.0
     cpp-options: -Dstan
 

plugins/hls-stan-plugin/hls-stan-plugin.cabal

@@ -23,6 +23,10 @@ flag pedantic
 
 
 library
+  if impl(ghc <= 8.6) || impl(ghc >= 9.0)
+    buildable: False
+  else
+    buildable: True
   exposed-modules:    Ide.Plugin.Stan
   hs-source-dirs:     src
   build-depends:
@@ -50,6 +54,10 @@ library
     OverloadedStrings
 
 test-suite test
+  if impl(ghc <= 8.6) || impl(ghc >= 9.0)
+    buildable: False
+  else
+    buildable: True
   type:             exitcode-stdio-1.0
   default-language: Haskell2010
   hs-source-dirs:   test