gnu: Define $CC to placate 'g-ir-scanner'.

* gnu/packages/glib.scm (telepathy-glib)[arguments]: New field.
* gnu/packages/gnome.scm (json-glib)[arguments]: New field.

gnu/packages/glib.scm

@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2013, 2014 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2013, 2014, 2015 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2013, 2015 Andreas Enge <andreas@enge.fr>
 ;;; Copyright © 2013 Nikita Karetnikov <nikita@karetnikov.org>
 ;;; Copyright © 2014 Mark H Weaver <mhw@netris.org>
@@ -536,6 +536,14 @@ useful for C++.")
         (base32
          "1symyzbjmxvksn2ifdkk50lafjm2llf2sbmky062gq2pz3cg23cy"))))
     (build-system gnu-build-system)
+    (arguments
+     '(#:phases (alist-cons-before
+                 'build 'set-cc
+                 (lambda _
+                   ;; Set $CC so that g-ir-scanner works.
+                   (setenv "CC" "gcc")
+                   #t)
+                 %standard-phases)))
     (native-inputs
      `(("glib" ,glib "bin") ; uses glib-mkenums
        ("pkg-config" ,pkg-config)

gnu/packages/gnome.scm

@@ -1460,12 +1460,20 @@ configuration storage systems.")
                (base32
                 "02k66lpc4cmgygj66n8zcy59bggy7yzm3v4hni9xqplgva9d2yw8"))))
     (build-system gnu-build-system)
+    (arguments
+     '(#:phases (alist-cons-before
+                 'build 'set-cc
+                 (lambda _
+                   ;; Set $CC so that g-ir-scanner works.
+                   (setenv "CC" "gcc")
+                   #t)
+                 %standard-phases)))
     (native-inputs
-     `(("glib" ,glib "bin") ; for glib-mkenums and glib-genmarshal
+     `(("glib" ,glib "bin")              ;for glib-mkenums and glib-genmarshal
        ("gobject-introspection" ,gobject-introspection)
        ("pkg-config" ,pkg-config)))
     (propagated-inputs
-     `(("glib" ,glib))) ; according to json-glib-1.0.pc
+     `(("glib" ,glib)))                         ;according to json-glib-1.0.pc
     (home-page "https://wiki.gnome.org/Projects/JsonGlib")
     (synopsis "Compiler for the GObject type system")
     (description "JSON-GLib is a C library based on GLib providing