gnu: Add rust-target-build-utils-0.3.

* gnu/packages/crates-io.scm (rust-target-build-utils-0.3):
New variable.

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

gnu/packages/crates-io.scm

@@ -16127,6 +16127,32 @@ memory all at once.")
      "This package provides a small wrapper around option.")
     (license (list license:asl2.0 license:expat))))
 
+(define-public rust-target-build-utils-0.3
+  (package
+    (name "rust-target-build-utils")
+    (version "0.3.1")
+    (source
+     (origin
+       (method url-fetch)
+       (uri (crate-uri "target_build_utils" version))
+       (file-name
+        (string-append name "-" version ".tar.gz"))
+       (sha256
+        (base32
+         "0p7713x4bpbwi11l196z1mi8ym8qj1cdnab1mm2ffpm2wi516g81"))))
+    (build-system cargo-build-system)
+    (arguments
+     `(#:cargo-inputs
+       (("rust-phf" ,rust-phf-0.7)
+        ("rust-serde-json" ,rust-serde-json-0.9)
+        ("rust-phf-codegen" ,rust-phf-codegen-0.7))))
+    (home-page "https://github.com/nagisa/target_build_utils.rs")
+    (synopsis "Rust utility to handle TARGET environment variable")
+    (description
+     "Utility crate to handle the @code{TARGET} environment variable passed into
+@code{build.rs} scripts.")
+    (license (list license:isc license:asl2.0))))
+
 (define-public rust-tempdir-0.3
   (package
     (name "rust-tempdir")