gnu: glibc-utf8-locales: Reintroduce input labels.

Since 2f73ea3487,
‘make-glibc-utf8-locales’ couldn’t be passed a package with a name other
than “glibc” (in particular “glibc-hurd”) since the builder expects the
name “glibc” in ‘%build-inputs’.

* gnu/packages/base.scm (make-glibc-utf8-locales): Reintroduce labels in
‘native-inputs’.

gnu/packages/base.scm

@@ -1382,7 +1382,9 @@ (define file
                                                          locale ".UTF-8")))
                                ',locales)
                      #t))))
-    (native-inputs (list glibc gzip))
+    (native-inputs
+     `(("glibc" ,glibc)
+       ("gzip" ,gzip)))
     (synopsis (if default-locales?
                   (P_ "Small sample of UTF-8 locales")
                   (P_ "Customized sample of UTF-8 locales")))