tools: add zip utility

One image requires a zip compressed image, so add the zip util found in
the packages feed, and extend it with some useful debian patches.

Signed-off-by: Mathias Kresin <dev@kresin.me>

tools/zip/patches/010-remove-build-date.patch

@@ -0,0 +1,15 @@
+From: Santiago Vila <sanvila@debian.org>
+Subject: Remove (optional) build date to make the build reproducible
+Bug-Debian: http://bugs.debian.org/779042
+
+--- a/unix/unix.c
++++ b/unix/unix.c
+@@ -1020,7 +1020,7 @@ void version_local()
+ 
+ 
+ /* Define the compile date string */
+-#ifdef __DATE__
++#if 0
+ #  define COMPILE_DATE " on " __DATE__
+ #else
+ #  define COMPILE_DATE ""