gnu: ruby-webrick: Update to 1.8.1.

* gnu/packages/ruby.scm (ruby-webrick): Update to 1.8.1.
[source]: Use git.
[arguments]: New field.

gnu/packages/ruby.scm

@@ -13616,14 +13616,26 @@ interface for the Sentry error logger.")
 (define-public ruby-webrick
   (package
     (name "ruby-webrick")
-    (version "1.7.0")
-    (source
-      (origin
-        (method url-fetch)
-        (uri (rubygems-uri "webrick" version))
-        (sha256
-          (base32 "1d4cvgmxhfczxiq5fr534lmizkhigd15bsx5719r5ds7k7ivisc7"))))
+    (version "1.8.1")
+    (source (origin
+              (method git-fetch)        ;for tests
+              (uri (git-reference
+                    (url "https://github.com/ruby/webrick")
+                    (commit (string-append "v" version))))
+              (file-name (git-file-name name version))
+              (sha256
+               (base32
+                "1xb0mk3cghdir65nmj0mblprbf21blli7267b6yyvxclh307yp6s"))))
     (build-system ruby-build-system)
+    (arguments
+     (list #:phases
+           #~(modify-phases %standard-phases
+               (add-after 'extract-gemspec 'delete-problematic-tests
+                 (lambda _
+                   ;; The httresponse tests fail for
+                   ;; unknown reasons (see:
+                   ;; https://github.com/ruby/webrick/issues/112).
+                   (delete-file "test/webrick/test_httpresponse.rb"))))))
     (home-page "https://github.com/ruby/webrick")
     (synopsis "HTTP server toolkit")
     (description "WEBrick is an HTTP server toolkit that can be configured as an