fix brew linux

Author: pete911

.goreleaser.yml

@@ -42,7 +42,7 @@ homebrew_casks:
     hooks:
        post:
          install: |
-           if system_command("/usr/bin/xattr", args: ["-h"]).exit_status == 0
+           if OS.mac?
              system_command "/usr/bin/xattr", args: ["-dr", "com.apple.quarantine", "#{staged_path}/ipcalc"]
            end