configure: Fix build with capabilities Since commit 417c9d72d48275d19c60861896efd4962d21aca2 all configure tests normally run with -Werror. Some of these tests now fail because they raised a compiler warning. This patch fixes support for capabilities. Signed-off-by: Stefan Weil <sw@weilnetz.de> Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>