Allow debugging patching failures

Closes Homebrew/homebrew#33056.

Library/Homebrew/debrew.rb

@@ -21,6 +21,10 @@ module Debrew
       Debrew.debrew { super }
     end
 
+    def patch
+      Debrew.debrew { super }
+    end
+
     def test
       Debrew.debrew { super }
     end

Library/Homebrew/patch.rb

@@ -128,7 +128,7 @@ class ExternalPatch
     resource.unpack do
       # Assumption: the only file in the staging directory is the patch
       patchfile = Pathname.pwd.children.first
-      safe_system "/usr/bin/patch", "-g", "0", "-f", "-d", dir, "-#{strip}", "-i", patchfile
+      dir.cd { safe_system "/usr/bin/patch", "-g", "0", "-f", "-#{strip}", "-i", patchfile }
     end
   end