Helper for packaging/grabbing osx apps; use it for OBS, keycastr, vlc

nix/system/worktop/makeApp.nix

@@ -0,0 +1,51 @@
+{ name
+, appname ? name
+, version
+, src
+, sourceRoot ? "."
+, # from nix
+  pkgs
+, stdenv
+, unzip
+, ...
+}:
+if stdenv.isDarwin then
+  pkgs.stdenv.mkDerivation
+  {
+    name = "${name}-${version}";
+    version = "${version}";
+    src = src;
+
+    sourceRoot = "${appname}.app";
+    phases = [ "unpackPhase" "installPhase" ];
+    unpackCmd = ''
+      echo "File to unpack: $curSrc"
+      if ! [[ "$curSrc" =~ \.dmg$ ]]; then return 1; fi
+      mnt=$(mktemp -d -t ci-XXXXXXXXXX)
+
+      function finish {
+        echo "Detaching $mnt"
+        /usr/bin/hdiutil detach $mnt -force
+        rm -rf $mnt
+      }
+      trap finish EXIT
+
+      echo "Attaching $mnt"
+      /usr/bin/hdiutil attach -nobrowse -readonly $src -mountpoint $mnt
+
+      echo "What's in the mount dir"?
+      ls -la $mnt/
+
+      echo "Copying contents"
+      shopt -s extglob
+      DEST="$PWD"
+      (cd "$mnt"; cp -a !(Applications) "$DEST/")
+    '';
+    nativeBuildInputs = [ pkgs.unzip ];
+    installPhase = ''
+      mkdir -p $out/Applications/${appname}.app
+      cp -a ./. $out/Applications/${appname}.app/
+    '';
+  }
+else
+  { }