rubocops/cask: Enforce the order of on_#{arch} blocks

- These were previously being manually fixed which is time maintainers
  could have spent fixing more important problems.
- I don't work with Casks much at all, so I was unsure as to what the
  existing "arch" and "on_arch_conditional" parts were, if they're
  deprecated or if things were eventually going to migrate to
  `on_#{arch}` blocks?

Library/Homebrew/rubocops/cask/constants/stanza.rb

@@ -6,7 +6,7 @@ module RuboCop
     # Constants available globally for use in all cask cops.
     module Constants
       STANZA_GROUPS = [
-        [:arch, :on_arch_conditional],
+        [:on_arm, :on_intel, :arch, :on_arch_conditional],
         [:version, :sha256],
         [:language],
         [:url, :appcast, :name, :desc, :homepage],

Library/Homebrew/test/rubocops/cask/stanza_order_spec.rb

@@ -474,4 +474,65 @@ describe RuboCop::Cop::Cask::StanzaOrder do
 
     include_examples "does not report any offenses"
   end
+
+  context "when `on_arch` blocks are out of order" do
+    let(:source) do
+      <<~CASK
+        cask 'foo' do
+          on_intel do
+            url "https://foo.brew.sh/foo-intel.zip"
+            sha256 :no_check
+            version :latest
+          end
+
+          on_arm do
+            url "https://foo.brew.sh/foo-arm.zip"
+            sha256 :no_check
+            version :latest
+          end
+
+          name "Foo"
+        end
+      CASK
+    end
+
+    let(:expected_offenses) do
+      [{
+        message:  "`on_intel` stanza out of order",
+        severity: :convention,
+        line:     2,
+        column:   2,
+        source:   "on_intel do\n    url \"https://foo.brew.sh/foo-intel.zip\"\n    sha256 :no_check\n    version :latest\n  end", # rubocop:disable Layout/LineLength
+      }, {
+        message:  "`on_arm` stanza out of order",
+        severity: :convention,
+        line:     8,
+        column:   2,
+        source:   "on_arm do\n    url \"https://foo.brew.sh/foo-arm.zip\"\n    sha256 :no_check\n    version :latest\n  end", # rubocop:disable Layout/LineLength
+      }]
+    end
+
+    let(:correct_source) do
+      <<~CASK
+        cask 'foo' do
+          on_arm do
+            url "https://foo.brew.sh/foo-arm.zip"
+            sha256 :no_check
+            version :latest
+          end
+
+          on_intel do
+            url "https://foo.brew.sh/foo-intel.zip"
+            sha256 :no_check
+            version :latest
+          end
+
+          name "Foo"
+        end
+      CASK
+    end
+
+    include_examples "reports offenses"
+    include_examples "autocorrects source"
+  end
 end