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
       "", ""
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<div class='path'>path: <a href='/guix/log/?id=4459c7859c286ab54fa3a9901c8a17591b04c516'>root</a>/<a href='/guix/log/build-aux?id=4459c7859c286ab54fa3a9901c8a17591b04c516'>build-aux</a>/<a href='/guix/log/build-aux/test-env.in?id=4459c7859c286ab54fa3a9901c8a17591b04c516'>test-env.in</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/build-aux/test-env.in?id=4459c7859c286ab54fa3a9901c8a17591b04c516&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2019-10-16 22:53:40 +0200'>2019-10-16</span></td><td><a href='/guix/commit/build-aux/test-env.in?id=a1aaca314ca94700ebe3449d6bd73522f2d243bc'>build: Remove references to 'NIX_LOCALSTATE_DIR'.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-10-16 22:53:40 +0200'>2019-10-16</span></td><td><a href='/guix/commit/build-aux/test-env.in?id=47e99e626b46b2fc433506a822d251de68ad6241'>daemon: Remove traces of 'NIX_ROOT_FINDER'.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-02-04 00:03:30 +0100'>2019-02-04</span></td><td><a href='/guix/commit/build-aux/test-env.in?id=a87d66f371da2a84d7bba1cae58b71c9c9af73aa'>daemon: Rename 'NIX_STATE_DIR' and 'NIX_DB_DIR' environment variables.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-05-13 23:16:16 +0200'>2018-05-13</span></td><td><a href='/guix/commit/build-aux/test-env.in?id=9e7b87ddc51c640c529d445e350c3d6ef43e301d'>build: 'test-env' does not 'guix download' non-existent files.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-04-22 23:50:49 +0200'>2018-04-22</span></td><td><a href='/guix/commit/build-aux/test-env.in?id=479c0e3f60f54e3c3a02f71efeb49119e20d2a96'>build: Fix possible race condition in 'test-env'.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2017-08-28 23:51:16 +0200'>2017-08-28</span></td><td><a href='/guix/commit/build-aux/test-env.in?id=4f024ef3181c5235ff11789e8c8f62722f974787'>build: Remove code to download the Guile bootstrap tarball.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>