remove unity and move most .nix to nixSupport

src/nixSupport/default.nix

@@ -0,0 +1,37 @@
+{
+  pkgs,
+  myCommitId,
+  ...
+}:
+let
+  xce = pkgs.callPackage ./xce.nix {
+    inherit pkgs myCommitId;
+    withDebug = false;
+    withAsan = false;
+    withoutDb = false;
+  };
+  xce_withoutdb = pkgs.callPackage ./xce.nix {
+    inherit pkgs myCommitId;
+    withDebug = false;
+    withAsan = false;
+    withoutDb = true;
+  };
+  xce_withoutdb_debug = pkgs.callPackage ./xce.nix {
+    inherit pkgs myCommitId;
+    withDebug = true;
+    withAsan = true;
+    withoutDb = true;
+  };
+  xce_debug = pkgs.callPackage ./xce.nix {
+    inherit pkgs myCommitId;
+    withDebug = true;
+    withAsan = true;
+    withoutDb = false;
+  };
+in
+{
+  xce = xce;
+  xce_debug = xce_debug;
+  xce_withoutdb = xce_withoutdb;
+  xce_withoutdb_debug = xce_withoutdb_debug;
+}

src/nixSupport/xce.nix

@@ -0,0 +1,56 @@
+{
+  lib,
+  stdenv,
+  pkgs,
+  myCommitId,
+  withDebug? false,
+  withAsan? false,
+  withoutDb? false,
+  ...
+}:
+
+stdenv.mkDerivation {
+
+  pname = "xce";
+  version = "0.0.1";
+
+  src = ./..;
+
+  nativeBuildInputs = [
+    pkgs.meson
+    pkgs.ninja
+    pkgs.capnproto
+    pkgs.pkg-config
+    pkgs.cmake
+    pkgs.go
+    pkgs.openssl
+    pkgs.libtirpc
+    pkgs.readline
+    pkgs.ncurses
+    pkgs.capnpc
+    pkgs.which
+    pkgs.findutils
+    pkgs.libuv
+    pkgs.elogind
+    pkgs.sqlite
+    pkgs.hwloc
+    pkgs.linux-pam
+    pkgs.zlog_with_pkgconf
+    pkgs.unity-test
+  ];
+
+  build-system = [ pkgs.meson ];
+
+  dontStrip = (withDebug || withAsan);
+  separateDebugInfo = (withDebug || withAsan);
+
+  impureEnvVars = [ "HOME" ];
+
+  mesonFlags =[
+    (lib.optional withDebug "-Dwith_debug=true")
+    (lib.optional withAsan "-Db_sanitize=address")
+    (lib.optional withoutDb "-Dwithout_db=true")
+    ("-Dcommit_id=" + myCommitId)
+    #    (lib.optional (!with_debug) "-Dbuildtype=release")
+  ];
+}