componnent/util-linux: Set minimum gcc version

util-linux needs gcc 8+ in order to avoid error:

libuuid/src/gen_uuid.c:536:33: error: initializer element is not constant

component/util-linux/buildout.cfg

@@ -6,6 +6,9 @@ extends =
   ../pkgconfig/buildout.cfg
   ../xz-utils/buildout.cfg
 
+[gcc]
+min_version = 8
+
 [util-linux]
 recipe = slapos.recipe.cmmi
 shared = true