gnu: Add rust-const-cstr.

* gnu/packages/crates-io.scm (rust-const-cstr-0.3): New variable.

gnu/packages/crates-io.scm

@@ -12260,6 +12260,25 @@ idiomatic wrappers for Mac OS X's CommonCrypto library.")
      "Common path finds the common prefix between a set of paths.")
     (license (list license:expat license:asl2.0))))
 
+(define-public rust-const-cstr-0.3
+  (package
+    (name "rust-const-cstr")
+    (version "0.3.0")
+    (source (origin
+              (method url-fetch)
+              (uri (crate-uri "const-cstr" version))
+              (file-name (string-append name "-" version ".tar.gz"))
+              (sha256
+               (base32
+                "19ij6m8s16d0i7vma535l7w4x8bcanjcxs7c6n7sci86ydghnggd"))))
+    (build-system cargo-build-system)
+    (home-page "https://github.com/cybergeek94/const-cstr")
+    (synopsis "Create static C-compatible strings from Rust string literals")
+    (description
+     "This crate lets you create static C-compatible strings from Rust string
+literals.")
+    (license (list license:expat license:asl2.0))))
+
 ;; This package requires features which are unavailable
 ;; on the stable releases of Rust.
 (define-public rust-compiler-builtins-0.1