postgresqlPackages.plv8: build on aarch64-linux

This might have been broken in days of yore, but it seems to work fine
now (reasonably so, since we use the system version of v8.)

Signed-off-by: Austin Seipp <[e-mail]>

pkgs/servers/sql/postgresql/ext/plv8/default.nix

···
     description = "V8 Engine Javascript Procedural Language add-on for PostgreSQL";
     homepage = "https://plv8.github.io/";
     maintainers = with maintainers; [ marsam ];
-    platforms = [ "x86_64-linux" ];
+    platforms = [ "x86_64-linux" "aarch64-linux" ];
     license = licenses.postgresql;
     broken = postgresql.jitSupport;
   };