gnu: json-c: Upgrade to 0.12.

* gnu/packages/pulseaudio.scm (json-c)[source]: Upgrade to 0.12.  Add
  'modules' and 'snippet' fields.

gnu/packages/pulseaudio.scm

@@ -113,14 +113,26 @@ rates. ")
 (define json-c
   (package
     (name "json-c")
-    (version "0.11")
+    (version "0.12")
     (source (origin
              (method url-fetch)
              (uri (string-append "https://s3.amazonaws.com/json-c_releases/releases/json-c-"
                                  version ".tar.gz"))
              (sha256
               (base32
-               "1324jja19jgsvcz9ij3nf4sgkrf4fg0ilw77vzqls3fw8m8wdpr8"))))
+               "0gwzic3ifg2d0w32ya3agpxh8i083cgvf7kmc51cnbgqnfr02300"))
+             (modules '((guix build utils)))
+             (snippet
+              '(begin
+                 ;; Somehow 'config.h.in' is older than
+                 ;; 'aclocal.m4', which would trigger a rule to
+                 ;; run 'autoheader'.
+                 (set-file-time "config.h.in"
+                                (stat "aclocal.m4"))
+
+                 ;; Don't try to build with -Werror.
+                 (substitute* (find-files "." "Makefile\\.in")
+                   (("-Werror") ""))))))
     (build-system gnu-build-system)
     (arguments '(#:parallel-build? #f
                  #:parallel-tests? #f))