gnu: inetutils: Do not refer to canonical coreutils.

Make sure not to retain a reference to the canonical coreutils package.  The
Guix System closure size would otherwise be increased by including references
to both canonical and non-canonical version of those packages.

* gnu/packages/admin.scm (inetutils)[inputs]: Add "coreutils",
[arguments]: and point to it with PATHDEF_CP variable.

gnu/packages/admin.scm

@@ -623,10 +623,16 @@ (define-public inetutils
                                    "--disable-uucpd"
                                    "--disable-whois")
                                  '()))
+       ;; Make sure that canonical "coreutils" package is not referred.
+       #:make-flags
+       (list (string-append "CPPFLAGS=-DPATHDEF_CP=\\\""
+                            (assoc-ref %build-inputs "coreutils*")
+                            "/bin/cp\\\""))
        ;; On some systems, 'libls.sh' may fail with an error such as:
        ;; "Failed to tell switch -a apart from -A".
        #:parallel-tests? #f))
-    (inputs `(("ncurses" ,ncurses)
+    (inputs `(("coreutils*" ,coreutils)
+              ("ncurses" ,ncurses)
               ("readline" ,readline)))        ;for 'ftp'
     (native-inputs (if (member (%current-system)
                                (package-supported-systems net-tools))