Fix for ghcjs

Author: hamishmack

overlays/ghcjs.nix

@@ -24,11 +24,35 @@ final: prev:
           shift
           ${final.buildPackages.nodejs-12_x}/bin/node $exe $@
         '') + "/bin/node-wrapper")];
-        packages.unix.components.library.preConfigure = ''
-          cp ${./patches/config.sub} config.sub
-          cp ${./patches/config.guess} config.guess
-          chmod +w config.*
-        '';
+
+        # Apply the patches that came with `ghcjs`
+        # Also add a "Keep alive" message to prevent hydra timeouts when hsc2hs runs
+        packages = pkgs.lib.genAttrs ["base" "directory" "filepath" "ghc-prim" "integer-gmp" "process" "template-haskell" "time" "unix" "Win32" ]
+          (name: {
+            components.library.preConfigure = ''
+              tr -d '\r' < ${name}.cabal > ${name}.cabal-new
+              mv ${name}.cabal-new ${name}.cabal
+              patch -p3 < ${pkgs.buildPackages.haskell-nix.compiler.${config.compiler.nix-name}.project.configured-src}/lib/patches/${name}.patch
+            '';
+            components.library.preBuild = ''
+              # Avoid timeouts while unix package runs hsc2hs (it does not print anything
+              # for more than 900 seconds).
+              KEEP_ALIVE_TMP=$(mktemp -d)
+              (
+                for n in {1..300}; do
+                  if [ ! -f $KEEP_ALIVE_TMP/done ]; then
+                    sleep 10
+                    if (( $n % 30 == 0 )); then
+                      echo "Keep alive: ${name} package build has been running for $(( n / 6 )) minute(s)"
+                    fi
+                  fi
+                done
+              ) &
+            '';
+            components.library.postBuild = ''
+              echo ok > $KEEP_ALIVE_TMP/done
+            '';
+          });
       })
     );
   });