Try #975:

ci.nix

@@ -24,14 +24,12 @@
     # Update supported-ghc-versions.md to reflect any changes made here.
     {
       ghc865 = true;
-    } // nixpkgs.lib.optionalAttrs (nixpkgsName == "R2003") {
+    } // nixpkgs.lib.optionalAttrs (nixpkgsName == "R2009") {
       ghc883 = false;
       ghc884 = true;
       ghc8101 = false;
       ghc8102 = true;
-      ghc810220201118 = false;
-    } // nixpkgs.lib.optionalAttrs (nixpkgsName == "R2009") {
-      ghc8102 = true;
+      ghc810220201118 = true;
     });
   systems = nixpkgs: nixpkgs.lib.filterAttrs (_: v: builtins.elem v supportedSystems) {
     # I wanted to take these from 'lib.systems.examples', but apparently there isn't one for linux!
@@ -42,7 +40,7 @@
     # We need to use the actual nixpkgs version we're working with here, since the values
     # of 'lib.systems.examples' are not understood between all versions
     let lib = nixpkgs.lib;
-    in lib.optionalAttrs (nixpkgsName == "R2003" && (__elem compiler-nix-name ["ghc865" "ghc884"])) {
+    in lib.optionalAttrs (nixpkgsName == "R2009" && (__elem compiler-nix-name ["ghc865" "ghc884"])) {
     inherit (lib.systems.examples) ghcjs;
   } // lib.optionalAttrs (system == "x86_64-linux" && (nixpkgsName == "R2009" || (!(__elem compiler-nix-name ["ghc8101" "ghc8102" "ghc810220201118"])))) {
     # Windows cross compilation is currently broken on macOS

lib/ghcjs-project.nix

@@ -76,6 +76,9 @@ let
         ++ lib.optionals stdenv.isDarwin [
           pkgs.buildPackages.gcc # https://github.com/ghcjs/ghcjs/issues/663
         ]
+        ++ lib.optionals (stdenv.isDarwin && isGhcjs88) [
+          pkgs.buildPackages.clang
+        ]
         ++ lib.optional isGhcjs88 [ emsdk ];
     # Configured the GHCJS source
     configured-src = pkgs.runCommand "configured-ghcjs-src" {