nongnu: rust-cbindgen-0.14.3: Rename and update it.

We do not want to interfere with upstreams rust-cbindgen for Icecat ESR.

* nongnu/packages/mozilla.scm (rust-cbindgen-0.14.3): Rename to
rust-cbindgen-firefox. Update to 0.15.0. Add comment why it's a
private variable.
(firefox)[native-inputs]: Adjust accordingly.

nongnu/packages/mozilla.scm

@@ -76,11 +76,13 @@
   #:use-module (gnu packages xdisorg)
   #:use-module (gnu packages xorg))
 
-(define rust-cbindgen-0.14.3
+;; Keep it private as we need it only for firefox. Upstream uses an older
+;; version for ESR based Icecat and Icedove. So we don't wanna mix them.
+(define rust-cbindgen-firefox
   (package
     (inherit rust-cbindgen-0.14)
     (name "rust-cbindgen")
-    (version "0.14.3")
+    (version "0.15.0")
     (source
      (origin
        (method url-fetch)
@@ -89,7 +91,7 @@
         (string-append name "-" version ".tar.gz"))
        (sha256
         (base32
-         "0n88s072g09sfnvsbbkfw0mgga15isj09wc6ak63brzjbmq3mq76"))))
+         "0dgf49zij9rxnf0lv4k5gcmx1mxcz16czkk6q63anz0xp8ds3xhx"))))
     (arguments
      ;; Cannot build with rust-1.39
      (cons* #:rust rust-1.43
@@ -406,7 +408,7 @@
        ("python" ,python)
        ("python2" ,python-2.7)
        ("rust" ,rust-1.43)
-       ("rust-cbindgen" ,rust-cbindgen-0.14.3)
+       ("rust-cbindgen" ,rust-cbindgen-firefox)
        ("which" ,which)
        ("yasm" ,yasm)))
     (home-page "https://mozilla.org/firefox/")