gnu: Add ghc-stringbuilder.

* gnu/packages/haskell.scm (ghc-stringbuilder): New variable.

gnu/packages/haskell.scm

@@ -664,6 +664,29 @@ bindings are a direct translation of the C bindings.")
 parts.")
     (license lgpl2.1)))
 
+(define-public ghc-stringbuilder
+  (package
+    (name "ghc-stringbuilder")
+    (version "0.5.0")
+    (source
+     (origin
+       (method url-fetch)
+       (uri (string-append
+             "http://hackage.haskell.org/package/stringbuilder/stringbuilder-"
+             version
+             ".tar.gz"))
+       (sha256
+        (base32
+         "1ap95xphqnrhv64c2a137wqslkdmb2jjd9ldb17gs1pw48k8hrl9"))))
+    (build-system haskell-build-system)
+    (arguments `(#:tests? #f)) ; FIXME: circular dependencies with tests
+                               ; enabled
+    (home-page "http://hackage.haskell.org/package/stringbuilder")
+    (synopsis "Writer monad for multi-line string literals")
+    (description "This package provides a writer monad for multi-line string
+literals.")
+    (license expat)))
+
 (define-public ghc-zlib
   (package
     (name "ghc-zlib")