transmission: fix building on Darwin

This sets "--disable-mac" so that we use GTK instead of the macOS
backend. The macOS backend should work but currently it breaks with xcbuild.

pkgs/applications/networking/p2p/transmission/default.nix

@@ -20,19 +20,22 @@ stdenv.mkDerivation rec {
     sha256 = "0pykmhi7pdmzq47glbj8i2im6iarp4wnj4l1pyvsrnba61f0939s";
   };
 
-  buildInputs = [ pkgconfig intltool file openssl curl libevent inotify-tools zlib ]
+  buildInputs = [ pkgconfig intltool file openssl curl libevent zlib ]
     ++ optionals enableGTK3 [ gtk3 makeWrapper ]
     ++ optionals enableSystemd [ systemd ]
+    ++ optionals stdenv.isLinux [ inotify-tools ];
 
   postPatch = ''
     substituteInPlace ./configure \
       --replace "libsystemd-daemon" "libsystemd" \
-      --replace "/usr/bin/file"     "${file}/bin/file"
+      --replace "/usr/bin/file"     "${file}/bin/file" \
+      --replace "test ! -d /Developer/SDKs/MacOSX10.5.sdk" "false"
   '';
 
   configureFlags = [
       ("--enable-cli=" + (if enableCli then "yes" else "no"))
       ("--enable-daemon=" + (if enableDaemon then "yes" else "no"))
+      "--disable-mac" # requires xcodebuild
     ]
     ++ optional enableSystemd "--with-systemd-daemon"
     ++ optional enableGTK3 "--with-gtk";
@@ -43,6 +46,8 @@ stdenv.mkDerivation rec {
       --prefix XDG_DATA_DIRS : "$GSETTINGS_SCHEMAS_PATH"
   '';
 
+  NIX_LDFLAGS = optionalString stdenv.isDarwin "-framework CoreFoundation";
+
   meta = with stdenv.lib; {
     description = "A fast, easy and free BitTorrent client";
     longDescription = ''
@@ -59,7 +64,7 @@ stdenv.mkDerivation rec {
     homepage = http://www.transmissionbt.com/;
     license = licenses.gpl2; # parts are under MIT
     maintainers = with maintainers; [ astsmtl vcunat wizeman ];
-    platforms = platforms.linux;
+    platforms = platforms.unix;
   };
 }