pharo: Tighten source and simplify meta.platforms

pkgs/development/pharo/vm/build-vm-legacy.nix

···
     license = stdenv.lib.licenses.mit;
     maintainers = [ stdenv.lib.maintainers.lukego ];
     # Pharo VM sources are packaged separately for darwin (OS X)
-    platforms = with stdenv.lib;
-                  intersectLists
-                    platforms.mesaPlatforms
-                    (subtractLists platforms.darwin platforms.unix);
+    platforms = stdenv.lib.filter
+      (system: with stdenv.lib.systems.elaborate { inherit system; };
+         isUnix && !isDarwin)
+      stdenv.lib.platforms.mesaPlatforms;
   };
 }

pkgs/development/pharo/wrapper/default.nix

···
 
 stdenv.mkDerivation rec {
   name = "pharo";
-  src = ./.;
+  src = ./pharo-vm.sh;
   inherit cog32 spur32 spur64 file;
   magic = ./magic;
   desktopItem = makeDesktopItem {
···
     categories = "Development;";
     mimeType = "application/x-pharo-image";
   };
+  unpackPhase = ''
+    cp $src ./pharo-vm.sh
+    sourceRoot=$PWD
+  '';
   buildPhase = ''
     substituteAllInPlace ./pharo-vm.sh
   '';
···
     license = stdenv.lib.licenses.mit;
     maintainers = [ stdenv.lib.maintainers.lukego ];
     # Pharo VM sources are packaged separately for darwin (OS X)
-    platforms = with stdenv.lib;
-                  intersectLists
-                    platforms.mesaPlatforms
-                    (subtractLists platforms.darwin platforms.unix);
+    platforms = stdenv.lib.filter
+      (system: with stdenv.lib.systems.elaborate { inherit system; };
+         isUnix && !isDarwin)
+      stdenv.lib.platforms.mesaPlatforms;
   };
 }