- resolveBuild: use plugin.dylib for darwin (was plugin.so)
- --bundle flag: build linux/amd64 + darwin/amd64 + windows/amd64,
package all binaries into a single .hmap with platforms field
- writePluginJSON: accept platforms []string for bundle manifest
- add createBundleHmap for zip entries with custom names
- add PlgConfig.IsLua() helper