Added ghcid-0.2

The .nix file was generated by cabal2nix. However, I still had to set
doCheck = false since some of the tests try to run `cabal repl` which
presupposes access to $HOME/.cabal and thus cannot be done from the Nix
sandbox where HOME = /homeless-shelter.

pkgs/development/tools/haskell/ghcid/default.nix

@@ -0,0 +1,20 @@
+# This file was auto-generated by cabal2nix. Please do NOT edit manually!
+
+{ cabal, cmdargs, filepath, tasty, tastyHunit, time }:
+
+cabal.mkDerivation (self: {
+  pname = "ghcid";
+  version = "0.2";
+  sha256 = "1g0jwj8s0rgwrdgyn6dwrqhf9v4kck5kfr4ggmp9c0mjjyfxq6pf";
+  isLibrary = true;
+  isExecutable = true;
+  buildDepends = [ cmdargs filepath time ];
+  testDepends = [ cmdargs filepath tasty tastyHunit time ];
+  doCheck = false;
+  meta = {
+    homepage = "https://github.com/ndmitchell/ghcid#readme";
+    description = "GHCi based bare bones IDE";
+    license = self.stdenv.lib.licenses.bsd3;
+    platforms = self.ghc.meta.platforms;
+  };
+})

pkgs/top-level/haskell-packages.nix

@@ -912,6 +912,7 @@ self : let callPackage = x : y : modifyPrio (newScope self x y); in
     cabal = self.cabal.override { enableLibraryProfiling = false; }; # pkg cannot be built with profiling enabled
   };
 
+  ghcid = callPackage ../development/tools/haskell/ghcid {};
 
   ghcServer = callPackage ../development/libraries/haskell/ghc-server {};