gnu: netperf: Update to 2.7.0-2.afc51ff.

* gnu/packages/networking.scm (netperf): Update to 2.7.0-2.afc51ff.
This fixes the build with current gcc.
[arguments]<#:configure-flags>: Extend CFLAGS.

Change-Id: I473d5c9773e47bc87530453ec8cc46570a2498f2
Signed-off-by: Andreas Enge <andreas@enge.fr>

gnu/packages/networking.scm

@@ -373,8 +373,8 @@ the RFC.")
 
 (define-public netperf
   (let ((version "2.7.0")
-        (revision "1")
-        (commit "3bc455b23f901dae377ca0a558e1e32aa56b31c4"))
+        (revision "2")
+        (commit "afc51ff9764741da4ed6702651fba9d9c23f8557"))
     (package
       (name "netperf")
       (version (git-version version revision commit))
@@ -387,13 +387,13 @@ the RFC.")
          (file-name (git-file-name name version))
          (sha256
           (base32
-           "1msbhbvf39r1a0c9b9myla5i6235fvnp7r6021fl8b5svxjbb0dk"))))
+           "1s7f1w0q9y15z8lhprh7irc1p9qgam140lvwncqk4gk74yvmcrcf"))))
       (build-system gnu-build-system)
       (arguments
        `(#:configure-flags
          ;; Without -fcommon the build fails on newer gcc.
          ;; See: https://gcc.gnu.org/gcc-10/porting_to.html
-         (list "CFLAGS=-fcommon"
+         (list "CFLAGS=-fcommon -D_GNU_SOURCE"
                ;; --enable-demo is needed for flent (not yet packaged).
                "--enable-demo")))
       (native-inputs