gnu: zyre: Kernel headers are system headers.

* gnu/packages/networking.scm (zyre)[arguments]: Add <#:make-flags>.

gnu/packages/networking.scm

@@ -2016,6 +2016,12 @@ remotely.")
                (base32
                 "0qz2730bng1gs9xbqxhkw88qbsmszgmmrl2g9k6xrg6r3bqvsdc7"))))
     (build-system gnu-build-system)
+    (arguments
+     `(;; Ensure the kernel headers are treated as system headers to suppress
+       ;; harmless -Werror=pedantic warnings.
+       #:make-flags (list (string-append "C_INCLUDE_PATH="
+                                         (assoc-ref %build-inputs "kernel-headers")
+                                         "/include"))))
     (inputs `(("zeromq" ,zeromq)
               ("czmq" ,czmq)
               ("libsodium" ,libsodium)))