source.mk: Rewrite

Upstream changed how releases are signed:

    http://lists.busybox.net/pipermail/busybox/2018-May/086438.html

Thread continues:

    http://lists.busybox.net/pipermail/busybox/2018-June/086478.html

1 files changed, 2 insertions, 1 deletions

diff --git a/control b/control
index 8a30af5..bef7f0e 100644
--- a/control
+++ b/control
@@ -1,3 +1,4 @@
 Maintainer: Patrick McDermott <patrick.mcdermott@libiquity.com>
-Build-Depends: opkhelper-3.0, config-busybox-${Host-Plat}
+Build-Depends: opkhelper-3.0, config-busybox-${Host-Plat},
+ gpg, dirmngr,
 Homepage: http://www.busybox.net/