apply extend/os to Cask::cmd::install#install_casks

Library/Homebrew/cask/cmd/install.rb

@@ -2,6 +2,7 @@
 # frozen_string_literal: true
 
 require "cask_dependent"
+require "extend/os/cask/cmd/install"
 
 module Cask
   class Cmd

Library/Homebrew/extend/os/cask/cmd/install.rb

@@ -0,0 +1,4 @@
+# typed: strict
+# frozen_string_literal: true
+
+require "extend/os/linux/cask/cmd/install" if OS.linux?

Library/Homebrew/extend/os/linux/cask/cmd/install.rb

@@ -0,0 +1,29 @@
+# typed: false
+# frozen_string_literal: true
+
+require "cask_dependent"
+
+module Cask
+  class Cmd
+    # Cask implementation of the `brew install` command.
+    #
+    # @api private
+    class Install < AbstractCommand
+      def self.install_casks(
+        _casks,
+        verbose: nil,
+        force: nil,
+        adopt: nil,
+        binaries: nil,
+        skip_cask_deps: nil,
+        require_sha: nil,
+        quarantine: nil,
+        quiet: nil,
+        zap: nil,
+        dry_run: nil
+      )
+        odie "Installing casks is supported only on macOS"
+      end
+    end
+  end
+end