gnu: Add rust-darling-0.9.

* gnu/packages/crates-io.scm (rust-darling-0.9): New variable.

Signed-off-by: Efraim Flashner <efraim@flashner.co.il>

gnu/packages/crates-io.scm

@@ -11931,6 +11931,30 @@ into structs when implementing custom derives.")
         ("rust-quote" ,rust-quote-1)
         ("rust-syn" ,rust-syn-1))))))
 
+(define-public rust-darling-0.9
+  (package
+    (inherit rust-darling-0.10)
+    (name "rust-darling")
+    (version "0.9.0")
+    (source
+      (origin
+        (method url-fetch)
+        (uri (crate-uri "darling" version))
+        (file-name
+         (string-append name "-" version ".tar.gz"))
+        (sha256
+         (base32
+          "1mnksf0i47pb7sxvi1iqfwmqy9iny0x8w56ilybpb431b46cpyzw"))))
+    (build-system cargo-build-system)
+    (arguments
+     `(#:cargo-inputs
+       (("rust-darling-core" ,rust-darling-core-0.9)
+        ("rust-darling-macro" ,rust-darling-macro-0.9))
+       #:cargo-development-inputs
+       (("rust-proc-macro2" ,rust-proc-macro2-0.4)
+        ("rust-quote" ,rust-quote-0.6)
+        ("rust-syn" ,rust-syn-0.15))))))
+
 (define-public rust-darling-core-0.12
   (package
     (name "rust-darling-core")