Try #1131:

builder/ghc-for-component-wrapper.nix

@@ -55,6 +55,10 @@ in runCommand "${componentName}-${ghc.name}-env" {
     # Replace the package database with the one from target package config.
     ln -s ${configFiles}/${packageCfgDir} $out/${packageCfgDir}
 
+    # now the tricky bit. For GHCJS (to make plugins work), we need a special
+    # file called ghc_libdir. That points to the build ghc's lib.
+    echo "${ghc.buildGHC or ghc}/lib/${(ghc.buildGHC or ghc).name}" > "${libDir}/ghc_libdir"
+
     # Wrap compiler executables with correct env variables.
     # The NIX_ variables are used by the patched Paths_ghc module.
 

compiler/ghcjs/ghcjs810-src.json

@@ -1,6 +1,6 @@
 {
   "url": "https://github.com/ghcjs/ghcjs",
-  "rev": "88fc8b7993a7c06fa1a71dd8ea494330108fa397",
-  "sha256": "066vqflvxfiiw8xy0fygdq8bdqmhdjfgpqibnyfcg0xlr9wsf2ld",
+  "rev": "ecb5954b98cdaeb3d4097401c9c3551e7a6f69ce",
+  "sha256": "09120brnd8n8psskq9f098n7wrlrbb2h7s703678a4gbl2xfglql",
   "fetchSubmodules": true
 }

overlays/bootstrap.nix

@@ -159,6 +159,7 @@ in {
                 ++ fromUntil "8.10.3" "8.10.5" ./patches/ghc/ghc-8.10.3-rts-make-markLiveObject-thread-safe.patch
                 ++ final.lib.optional (versionAtLeast "8.10.4" && final.targetPlatform.isWindows) ./patches/ghc/ghc-8.10-z-drive-fix.patch
                 ++ final.lib.optional (versionAtLeast "8.6.5") ./patches/ghc/ghc-8.10-windows-add-dependent-file.patch
+                ++ fromUntil "8.10.1" "9.0"    ./patches/ghc/Cabal-unbreak-GHCJS.patch
                 ;
         in ({
             ghc844 = final.callPackage ../compiler/ghc {

overlays/patches/ghc/Cabal-unbreak-GHCJS.patch

@@ -0,0 +1,20 @@
+diff --git a/libraries/Cabal/Cabal/Distribution/Simple/GHCJS.hs b/libraries/Cabal/Cabal/Distribution/Simple/GHCJS.hs
+index 4ad5bb18c..5db4d27e7 100644
+--- a/libraries/Cabal/Cabal/Distribution/Simple/GHCJS.hs
++++ b/libraries/Cabal/Cabal/Distribution/Simple/GHCJS.hs
+@@ -317,13 +317,10 @@ checkPackageDbStack :: Verbosity -> PackageDBStack -> IO ()
+ checkPackageDbStack _ (GlobalPackageDB:rest)
+   | GlobalPackageDB `notElem` rest = return ()
+ checkPackageDbStack verbosity rest
+-  | GlobalPackageDB `notElem` rest =
+-  die' verbosity $ "With current ghc versions the global package db is always used "
+-     ++ "and must be listed first. This ghc limitation may be lifted in "
+-     ++ "future, see http://ghc.haskell.org/trac/ghc/ticket/5977"
+-checkPackageDbStack verbosity _ =
++  | GlobalPackageDB `elem` rest =
+   die' verbosity $ "If the global package db is specified, it must be "
+      ++ "specified first and cannot be specified multiple times"
++checkPackageDbStack _ _ = return ()
+
+ getInstalledPackages' :: Verbosity -> [PackageDB] -> ProgramDb
+                       -> IO [(PackageDB, [InstalledPackageInfo])]

release.nix

@@ -1,7 +1,7 @@
 # 'supportedSystems' restricts the set of systems that we will evaluate for. Useful when you're evaluating
 # on a machine with e.g. no way to build the Darwin IFDs you need!
 { supportedSystems ? [ "x86_64-linux" "x86_64-darwin" ]
-, ifdLevel ? 3
+, ifdLevel ? 2
 , checkMaterialization ? false }:
 
 let