Revert "remove Nim-1.2.0 as it's part of NixOS 20.03"

This reverts commit bcfa50b0d0.

default.nix

@@ -15,6 +15,8 @@ self: super:
   easyhid = super.callPackage ./pkgs/easyhid/default.nix { };
   openphone = super.callPackage ./pkgs/openphone/default.nix { };
 
+  nim = super.callPackages ./pkgs/nim/default.nix { };
+
   shinto-cli = super.callPackage ./pkgs/shinto-cli { };
 
   ui = super.callPackage ./pkgs/nim-packages/ui.nix { };

pkgs/nim/default.nix

@@ -0,0 +1,69 @@
+# based on https://github.com/nim-lang/Nim/blob/v0.18.0/.travis.yml
+
+{ stdenv, lib, fetchurl, makeWrapper, openssl, pcre, readline,
+  boehmgc, sfml, sqlite }:
+
+stdenv.mkDerivation rec {
+  pname = "nim";
+  version = "1.2.0";
+
+  src = fetchurl {
+    url = "https://nim-lang.org/download/${pname}-${version}.tar.xz";
+    sha256 = "TpRYOjc5ZYIYBeZl4KBfUvthCRZnbtsJFIlBQVY3xXU=";
+  };
+
+  enableParallelBuilding = true;
+
+  NIX_LDFLAGS = "-lcrypto -lpcre -lreadline -lgc -lsqlite3";
+
+  # we could create a separate derivation for the "written in c" version of nim
+  # used for bootstrapping, but koch insists on moving the nim compiler around
+  # as part of building it, so it cannot be read-only
+
+  nativeBuildInputs = [
+    makeWrapper
+  ];
+
+  buildInputs = [
+    openssl pcre readline boehmgc sfml sqlite
+  ];
+
+  buildPhase = ''
+    runHook preBuild
+
+    # build.sh wants to write to $HOME/.cache
+    HOME=$TMPDIR
+    sh build.sh
+    ./bin/nim c koch
+    ./koch boot  -d:release \
+                 -d:useGnuReadline \
+                 ${lib.optionals (stdenv.isDarwin || stdenv.isLinux) "-d:nativeStacktrace"}
+    ./koch tools -d:release
+
+    runHook postBuild
+  '';
+
+  installPhase = ''
+    runHook preInstall
+
+    install -Dt $out/bin bin/* koch
+    ./koch install $out
+    mv $out/nim/bin/* $out/bin/ && rmdir $out/nim/bin
+    mv $out/nim/*     $out/     && rmdir $out/nim
+
+    # Fortify hardening appends -O2 to gcc flags which is unwanted for unoptimized nim builds.
+    wrapProgram $out/bin/nim \
+      --run 'NIX_HARDENING_ENABLE=''${NIX_HARDENING_ENABLE/fortify/}' \
+      --suffix PATH : ${lib.makeBinPath [ stdenv.cc ]}
+
+    runHook postInstall
+  '';
+
+  meta = with stdenv.lib; {
+    description = "Statically typed, imperative programming language";
+    homepage = "https://nim-lang.org/";
+    license = licenses.mit;
+    maintainers = with maintainers; [ ehmry ];
+    platforms = with platforms; linux ++ darwin; # arbitrary
+  };
+}