Copied from Debian.

From: Jérémy Bobbio <lunar@debian.org>
Subject: Remove build date
Bug-Debian: http://bugs.debian.org/782851
 In order to make unzip build reproducibly, we remove the
 (already optional) build date from the binary.

--- a/unix/unix.c
+++ b/unix/unix.c
@@ -1705,7 +1705,7 @@
 #endif /* Sun */
 #endif /* SGI */
 
-#ifdef __DATE__
+#if 0
       " on ", __DATE__
 #else
       "", ""