gnu: docker: Compile with seccomp enabled.

* gnu/packages/docker.scm (docker)[arguments]: Adjust custom 'configure
phase to enable seccomp support.

Signed-off-by: Efraim Flashner <efraim@flashner.co.il>

gnu/packages/docker.scm

@@ -520,6 +520,7 @@ (define-public docker
              #t))
          (replace 'configure
            (lambda _
+             (setenv "DOCKER_BUILDTAGS" "seccomp")
              (setenv "DOCKER_GITCOMMIT" (string-append "v" ,%docker-version))
              (setenv "VERSION" (string-append ,%docker-version "-ce"))
              ;; Automatically use bundled dependencies.