firedrake: Moved to new overlay system and shared sub-scope

Firedrake contains a ton of inter-connected dependencies, many of
which are either firedrake specific or forked versions of upstream
packages.  Cleaner to create a firedrake sub-scope for all these.

pkgs/firedrake/pulp.nix

@@ -0,0 +1,34 @@
+{ lib, fetchFromGitHub, pythonPackages
+, glpk, cbc }:
+
+pythonPackages.buildPythonPackage rec {
+  version = "1.6.4";
+  name = "PuLP-${version}";
+
+  src = fetchFromGitHub {
+    owner = "coin-or";
+    repo = "pulp";
+    rev = "${version}";
+    sha256 = "02i915ixrz66bpaka82j0x72kl76sr2b5xdx4ahwdlsffvmv9qnx";
+  };
+
+  buildInputs = [
+    glpk
+    cbc
+  ];
+
+  propagatedBuildInputs = [
+    pythonPackages.pyparsing
+  ];
+
+  postPatch = ''
+    sed -i -e 's|^CbcPath = .*$|CbcPath = ${cbc}/bin/cbc|' src/pulp/pulp.cfg.linux
+    sed -i -e 's|^GlpkPath = .*$|GlpkPath = ${glpk}/bin/glpsol|' src/pulp/pulp.cfg.linux
+  '';
+
+  meta = with lib; {
+    homepage = "https://github.com/coin-or/pulp";
+    description = "A python Linear Programming API.";
+    license = licenses.mit;
+  };
+}