gnu: Add rust-clang-sys-0.22.

* gnu/packages/crates-io.scm (rust-clang-sys-0.22): New variable.

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

gnu/packages/crates-io.scm

@@ -1855,6 +1855,36 @@ (define-public rust-clang-sys-0.26
                        (string-append clang "/lib")))
              #t)))))))
 
+(define-public rust-clang-sys-0.22
+  (package
+    (inherit rust-clang-sys-0.26)
+    (name "rust-clang-sys")
+    (version "0.22.0")
+    (source
+     (origin
+       (method url-fetch)
+       (uri (crate-uri "clang-sys" version))
+       (file-name
+        (string-append name "-" version ".tar.gz"))
+       (sha256
+        (base32
+         "0f65dw1ydnzq4wrv894fql78n4ikb53jjp53xck0s4hb64s1m6lk"))))
+    (build-system cargo-build-system)
+    (arguments
+     `(#:cargo-inputs
+       (("rust-clippy" ,rust-clippy-0.0)
+        ("rust-glob" ,rust-glob-0.2)
+        ("rust-libc" ,rust-libc-0.2)
+        ("rust-libloading" ,rust-libloading-0.5))
+       #:phases
+       (modify-phases %standard-phases
+         (add-after 'unpack 'set-environmental-variable
+           (lambda* (#:key inputs #:allow-other-keys)
+             (let ((clang (assoc-ref inputs "libclang")))
+               (setenv "LIBCLANG_PATH"
+                       (string-append clang "/lib")))
+             #t)))))))
+
 (define-public rust-clap-2
   (package
     (name "rust-clap")