Move Sandbox check to extend/os

Library/Homebrew/extend/os/mac/sandbox.rb

@@ -0,0 +1,9 @@
+# typed: strict
+# frozen_string_literal: true
+
+class Sandbox
+  sig { returns(T::Boolean) }
+  def self.available?
+    File.executable?(SANDBOX_EXEC)
+  end
+end

Library/Homebrew/extend/os/sandbox.rb

@@ -0,0 +1,4 @@
+# typed: strict
+# frozen_string_literal: true
+
+require "extend/os/mac/sandbox" if OS.mac?

Library/Homebrew/sandbox.rb

@@ -17,7 +17,7 @@ class Sandbox
 
   sig { returns(T::Boolean) }
   def self.available?
-    OS.mac? && File.executable?(SANDBOX_EXEC)
+    false
   end
 
   sig { void }
@@ -256,3 +256,5 @@ class Sandbox
   end
   private_constant :SandboxProfile
 end
+
+require "extend/os/sandbox"