gnu: Add rust-env-logger-0.7.

* gnu/packages/crates-io.scm (rust-env-logger-0.7): New variable.
(rust-env-logger-0.6): Inherit from rust-env-logger-0.7.

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

gnu/packages/crates-io.scm

@@ -2758,8 +2758,38 @@ Standard.")
      "Streaming transcoding for encoding_rs.")
     (license (list license:asl2.0 license:expat))))
 
+(define-public rust-env-logger-0.7
+  (package
+    (name "rust-env-logger")
+    (version "0.7.1")
+    (source
+     (origin
+       (method url-fetch)
+       (uri (crate-uri "env_logger" version))
+       (file-name
+        (string-append name "-" version ".tar.gz"))
+       (sha256
+        (base32
+         "0djx8h8xfib43g5w94r1m1mkky5spcw4wblzgnhiyg5vnfxknls4"))))
+    (build-system cargo-build-system)
+    (arguments
+     `(#:skip-build? #t
+       #:cargo-inputs
+       (("rust-atty" ,rust-atty-0.2)
+        ("rust-humantime" ,rust-humantime-1.3)
+        ("rust-log" ,rust-log-0.4)
+        ("rust-regex" ,rust-regex-1.1)
+        ("rust-termcolor" ,rust-termcolor-1.0))))
+    (home-page "https://github.com/sebasmagri/env_logger/")
+    (synopsis "Logging implementation for @code{log}")
+    (description
+     "This package provides a logging implementation for @code{log} which
+is configured via an environment variable.")
+    (license (list license:expat license:asl2.0))))
+
 (define-public rust-env-logger-0.6
   (package
+    (inherit rust-env-logger-0.7)
     (name "rust-env-logger")
     (version "0.6.2")
     (source
@@ -2771,7 +2801,6 @@ Standard.")
        (sha256
         (base32
          "1lx2s5nk96xx4i3m4zc4ghqgi8kb07dsnyiv8jk2clhax42dxz5a"))))
-    (build-system cargo-build-system)
     (arguments
      `(#:skip-build? #t
        #:cargo-inputs
@@ -2779,15 +2808,7 @@ Standard.")
         ("rust-humantime" ,rust-humantime-1.2)
         ("rust-log" ,rust-log-0.4)
         ("rust-regex" ,rust-regex-1.1)
-        ("rust-termcolor" ,rust-termcolor-1.0))))
-    (home-page
-     "https://github.com/sebasmagri/env_logger/")
-    (synopsis
-     "Logging implementation for @code{log}")
-    (description
-     "This package provides a logging implementation for @code{log} which
-is configured via an environment variable.")
-    (license (list license:expat license:asl2.0))))
+        ("rust-termcolor" ,rust-termcolor-1.0))))))
 
 (define-public rust-envmnt-0.6
   (package