docker: Add "--enable-werror" to configure command line

We don't have .git in the docker checkout, add this to enable -Werror
explicitly.

Signed-off-by: Fam Zheng <famz@redhat.com>
Message-id: 1469453510-658-1-git-send-email-famz@redhat.com

tests/docker/common.rc

@@ -24,6 +24,7 @@ requires()
 build_qemu()
 {
     $QEMU_SRC/configure \
+        --enable-werror \
         ${TARGET_LIST:+"--target-list=${TARGET_LIST}"} \
         --prefix="$PWD/install" \
         $EXTRA_CONFIGURE_OPTS \