cask/audit: Pass a URL's referer through to cURL

- Some casks have URL arguments like "referer" (spelled wrong, that's
  intentional in the HTTP spec).
- The audit for one such cask, `iThoughtsX`, was failing because the
  "referer" wasn't getting passed through to cURL so the access would
  404.

----

Before:

```
❯ brew audit --cask --online --appcast --signing 'ithoughtsx'
[...]
audit for ithoughtsx: failed
 - The binary URL https://cdn.toketaware.com?download=iThoughtsX.zip is not reachable (HTTP status code 404)
 - Version '9.2.0' differs from '9.3.0' retrieved by livecheck.
 - Version '9.2.0' differs from '9.3.0' retrieved by livecheck.
Error: 2 problems in 1 cask detected
```

After:

```
❯ brew audit --cask --online --appcast --signing 'ithoughtsx'
[...]
audit for ithoughtsx: failed
 - Version '9.2.0' differs from '9.3.0' retrieved by livecheck.
 - Version '9.2.0' differs from '9.3.0' retrieved by livecheck.
Error: 1 problem in 1 cask detected
```

Library/Homebrew/cask/audit.rb

@@ -805,7 +805,7 @@ module Cask
 
       if cask.url && !cask.url.using
         validate_url_for_https_availability(cask.url, "binary URL", cask.token, cask.tap,
-                                            user_agents: [cask.url.user_agent])
+                                            user_agents: [cask.url.user_agent], referer: cask.url&.referer)
       end
 
       if cask.appcast && appcast?

Library/Homebrew/test/utils/curl_spec.rb

@@ -371,6 +371,14 @@ describe "Utils::Curl" do
       expect { curl_args(*args, retry_max_time: "test") }.to raise_error(TypeError)
     end
 
+    it "uses `--referer` when :referer is present" do
+      expect(curl_args(*args, referer: "https://brew.sh").join(" ")).to include("--referer https://brew.sh")
+    end
+
+    it "doesn't use `--referer` when :referer is nil" do
+      expect(curl_args(*args, referer: nil).join(" ")).not_to include("--referer")
+    end
+
     it "uses HOMEBREW_USER_AGENT_FAKE_SAFARI when `:user_agent` is `:browser` or `:fake`" do
       expect(curl_args(*args, user_agent: :browser).join(" "))
         .to include("--user-agent #{HOMEBREW_USER_AGENT_FAKE_SAFARI}")

Library/Homebrew/utils/curl.rb

@@ -56,6 +56,7 @@ module Utils
         show_output:     T.nilable(T::Boolean),
         show_error:      T.nilable(T::Boolean),
         user_agent:      T.any(String, Symbol, NilClass),
+        referer:         T.nilable(String),
       ).returns(T::Array[T.untyped])
     }
     def curl_args(
@@ -66,7 +67,8 @@ module Utils
       retry_max_time: nil,
       show_output: false,
       show_error: true,
-      user_agent: nil
+      user_agent: nil,
+      referer: nil
     )
       args = []
 
@@ -108,6 +110,8 @@ module Utils
 
       args << "--retry-max-time" << retry_max_time.round if retry_max_time.present?
 
+      args << "--referer" << referer if referer.present?
+
       args + extra_args
     end
 
@@ -238,7 +242,7 @@ module Utils
       set_cookie_header.compact.any? { |cookie| cookie.match?(/^(visid_incap|incap_ses)_/i) }
     end
 
-    def curl_check_http_content(url, url_type, specs: {}, user_agents: [:default],
+    def curl_check_http_content(url, url_type, specs: {}, user_agents: [:default], referer: nil,
                                 check_content: false, strict: false, use_homebrew_curl: false)
       return unless url.start_with? "http"
 
@@ -254,6 +258,7 @@ module Utils
               hash_needed:       true,
               use_homebrew_curl: use_homebrew_curl,
               user_agent:        user_agent,
+              referer:           referer,
             )
           rescue Timeout::Error
             next
@@ -276,6 +281,7 @@ module Utils
             hash_needed:       hash_needed,
             use_homebrew_curl: use_homebrew_curl,
             user_agent:        user_agent,
+            referer:           referer,
           )
         break if http_status_ok?(details[:status_code])
       end
@@ -364,7 +370,7 @@ module Utils
 
     def curl_http_content_headers_and_checksum(
       url, specs: {}, hash_needed: false,
-      use_homebrew_curl: false, user_agent: :default
+      use_homebrew_curl: false, user_agent: :default, referer: nil
     )
       file = Tempfile.new.tap(&:close)
 
@@ -385,7 +391,8 @@ module Utils
         connect_timeout:   15,
         max_time:          max_time,
         retry_max_time:    max_time,
-        user_agent:        user_agent
+        user_agent:        user_agent,
+        referer:           referer
       )
 
       parsed_output = parse_curl_output(output)