junixsocket: Support Darwin

Patch borrowed from Rob Vermaas.

pkgs/development/libraries/java/junixsocket/default.nix

@@ -8,11 +8,15 @@ stdenv.mkDerivation rec {
     sha256 = "0c6p8vmiv5nk8i6g1hgivnl3mpb2k3lhjjz0ss9dlirisfrxf1ym";
   };
 
+  patches = [ ./darwin.patch ];
+
   buildInputs = [ ant jdk junit ];
 
   preConfigure =
     ''
-      sed -i 's|/usr/bin/||' build.xml
+      substituteInPlace build.xml \
+        --replace /usr/bin/ "" \
+        --replace macosx darwin
       substituteInPlace src/main/org/newsclub/net/unix/NativeUnixSocketConfig.java \
         --replace /opt/newsclub/lib-native $out/lib
     '';
@@ -20,8 +24,10 @@ stdenv.mkDerivation rec {
   buildPhase = "ant";
 
   ANT_ARGS =
-    "-Dskip32=true -Dant.build.javac.source=1.6"
-    + stdenv.lib.optionalString stdenv.isDarwin " -DisMac=true";
+    # Note that our OpenJDK on Darwin is currently 32-bit, so we have to build a 32-bit dylib.
+    (if stdenv.is64bit && !stdenv.isDarwin then [ "-Dskip32=true" ] else [ "-Dskip64=true" ])
+    ++ [ "-Dgcc=cc" "-Dant.build.javac.source=1.6" ]
+    ++ stdenv.lib.optional stdenv.isDarwin "-DisMac=true";
 
   installPhase =
     ''
@@ -34,6 +40,6 @@ stdenv.mkDerivation rec {
     description = "A Java/JNI library for using Unix Domain Sockets from Java";
     homepage = https://code.google.com/p/junixsocket/;
     license = stdenv.lib.licenses.asl20;
-    platforms = stdenv.lib.platforms.linux;
+    platforms = stdenv.lib.platforms.linux ++ stdenv.lib.platforms.darwin;
   };
 }