gnu: graphene: Fix build on armhf-linux.

* gnu/packages/gtk.scm (graphene)[arguments]: When building for
armhf-linux add a configure-flag to disable neon optimizations.

Change-Id: I42b412d3f7536180e959e268b68f2c292edda749

gnu/packages/gtk.scm

@@ -2424,6 +2424,11 @@ Parcellite and adds bugfixes and features.")
        #:configure-flags
        (list
         "-Dinstalled_tests=false"
+        ;; Armhf with neon in graphene segfaulting is a known issue.
+        ;; https://github.com/ebassi/graphene/issues/215
+        ,@(if (target-arm32?)
+              '("-Darm_neon=false")
+              '())
         ,@(if (%current-target-system)
               ;; Introspection requires running binaries for 'host' on 'build'.
               '("-Dintrospection=disabled")