adds support to build emscripten packages using nix:

example usage:

- nix-env -I nixpkgs=../somewhere/nixpkgs -f default.nix -iA emscriptenPackages.libxml2
- nix-env -I nixpkgs=../somewhere/nixpkgs -f default.nix -iA emscriptenPackages.json_c
- nix-env -I nixpkgs=../somewhere/nixpkgs -f default.nix -iA emscriptenPackages.zlib
- nix-env -I nixpkgs=../somewhere/nixpkgs -f default.nix -iA emscriptenPackages.xmlmirror

pkgs/development/em-modules/generic/default.nix

@@ -0,0 +1,59 @@
+{ pkgs, lib, emscripten }:
+
+{ buildInputs ? [], nativeBuildInputs ? []
+
+, enableParallelBuilding ? true
+
+, meta ? {}, ... } @ args:
+
+pkgs.stdenv.mkDerivation (
+  args // 
+  {
+
+  name = "emscripten-${args.name}";
+  buildInputs = [ emscripten ] ++ buildInputs;
+  nativeBuildInputs = [ emscripten ] ++ nativeBuildInputs;
+
+  # fake conftest results with emscripten's python magic
+  EMCONFIGURE_JS=2;
+
+  configurePhase = args.configurePhase or ''
+    # FIXME: Some tests require writing at $HOME
+    HOME=$TMPDIR
+    runHook preConfigure
+
+    # probably requires autotools as dependency
+    ./autogen.sh
+    emconfigure ./configure --prefix=$out
+
+    runHook postConfigure
+  '';
+
+  buildPhase = args.buildPhase or ''
+    runHook preBuild
+
+    HOME=$TMPDIR
+    emmake make
+
+    runHook postBuild
+  '';
+
+  checkPhase = args.checkPhase or ''
+    runHook preCheck
+
+    runHook postCheck
+  '';
+
+  enableParallelBuilding = args.enableParallelBuilding or true;
+
+  meta = {
+    # Add default meta information
+    platforms = lib.platforms.all;
+    # Do not build this automatically
+    hydraPlatforms = [];
+  } // meta // {
+    # add an extra maintainer to every package
+    maintainers = (meta.maintainers or []) ++
+                  [ lib.maintainers.qknight ];
+  };
+})

pkgs/top-level/all-packages.nix

@@ -1402,10 +1402,19 @@ in
 
   eid-viewer = callPackage ../tools/security/eid-viewer { };
 
+  ### DEVELOPMENT / EMSCRIPTEN
+
+  buildEmscriptenPackage = callPackage ../development/em-modules/generic { };
+
   emscripten = callPackage ../development/compilers/emscripten { };
 
   emscriptenfastcomp = callPackage ../development/compilers/emscripten-fastcomp { };
 
+  emscriptenPackages = recurseIntoAttrs (callPackage ./emscripten-packages.nix { });
+
+  emscriptenStdenv = stdenv // { mkDerivation = buildEmscriptenPackage; };
+
+
   efibootmgr = callPackage ../tools/system/efibootmgr { };
 
   efivar = callPackage ../tools/system/efivar { };

pkgs/top-level/emscripten-packages.nix

@@ -0,0 +1,103 @@
+{ pkgs }:
+
+# emscripten toolchain abstraction for nix
+# https://github.com/NixOS/nixpkgs/pull/16208
+
+with pkgs; rec {
+  json_c = pkgs.json_c.override {
+    stdenv = emscriptenStdenv;
+  };
+  
+  libxml2 = (pkgs.libxml2.override {
+    stdenv = emscriptenStdenv;
+    supportPython = false;
+  }).overrideDerivation
+    (old: { 
+      buildInputs = old.buildInputs ++ [ autoreconfHook pkgconfig zlib nodejs ];
+      nativeBuildInputs = old.nativeBuildInputs ++ [ zlib pkgconfig ];
+      # just override it with nothing so it does not fail
+      autoreconfPhase = "echo autoreconfPhase not used..."; 
+      checkPhase = ''
+        echo "================= testing xmllint using node ================="
+        emcc -O2 -s EMULATE_FUNCTION_POINTER_CASTS=1 xmllint.o \
+        ./.libs/libxml2.a `pkg-config zlib --cflags` `pkg-config zlib --libs` -o ./xmllint.test.js \
+        --embed-file ./test/xmlid/id_err1.xml  
+        # test/xmlid/id_err2.xml:3: validity error : xml:id : attribute type should be ID
+        # <!ATTLIST foo xml:id CDATA #IMPLIED>
+        #                                    ^
+        node ./xmllint.test.js --noout test/xmlid/id_err1.xml 2>&1  | grep 0bar   
+        if [ $? -ne 0 ]; then
+          echo "xmllint unit test failed, please fix this package"
+          exit 1;
+        else
+          echo "since there is no stupid text containing 'foo xml:id' it seems to work! very good."
+        fi
+        echo "================= /testing xmllint using node ================="
+      '';
+    });            
+  
+  xmlmirror = buildEmscriptenPackage rec {
+    name = "xmlmirror";
+
+    buildInputs = [ autoconf automake libtool pkgconfig gnumake libxml2 nodejs 
+       python openjdk json_c zlib ];
+
+    src = fetchgit {
+      url = "https://gitlab.com/odfplugfest/xmlmirror.git";
+      rev = "4fd7e86f7c9526b8f4c1733e5c8b45175860a8fd";
+      sha256 = "1jasdqnbdnb83wbcnyrp32f36w3xwhwp0wq8lwwmhqagxrij1r4b";
+    };
+     
+    configurePhase = ''
+      rm -f fastXmlLint.js*
+    '';
+    
+    buildPhase = ''
+      HOME=$TMPDIR
+      make -f Makefile.emEnv
+    '';
+    
+    outputs = [ "out" "doc" ];
+    
+    installPhase = ''
+      mkdir -p $out/share
+      mkdir -p $doc
+      
+      cp Demo* $out/share
+      cp -R codemirror-5.12 $out/share
+      cp fastXmlLint.js* $out/share
+      cp *.xsd $out/share
+      cp *.js $out/share
+      cp *.xhtml $out/share
+      cp *.html $out/share
+      cp *.json $out/share
+      cp *.rng $out/share
+      cp README.md $doc/
+    '';
+    
+    postInstall = ''
+    '';
+  };  
+
+  zlib = (pkgs.zlib.override {
+    stdenv = emscriptenStdenv;
+  }).overrideDerivation
+    (old: { 
+      configurePhase = ''
+        # FIXME: Some tests require writing at $HOME
+        HOME=$TMPDIR
+        runHook preConfigure
+
+        emconfigure ./configure --prefix=$out
+
+        runHook postConfigure
+      '';
+      postPatch = stdenv.lib.optionalString stdenv.isDarwin ''
+        substituteInPlace configure \
+          --replace '/usr/bin/libtool' 'ar' \
+          --replace 'AR="libtool"' 'AR="ar"' \
+          --replace 'ARFLAGS="-o"' 'ARFLAGS="-r"'
+      '';
+    }); 
+  
+}