This following patch was originally found at the debian mingw-w64 team's
mingw-w64 repo located here:
https://salsa.debian.org/mingw-w64-team/mingw-w64.git

Invoke the following in the aforementioned repo to see the original patch:

  $ git show 4974e2c:debian/patches/reproducible-gendef.patch

Description: Drop __DATE__ from gendef
Author: Stephen Kitt <skitt@debian.org>

This allows gendef to be built reproducibly.

--- a/mingw-w64-tools/gendef/src/gendef.c
+++ b/mingw-w64-tools/gendef/src/gendef.c
@@ -196,7 +196,6 @@
                    "  By default, the output files are named after their DLL counterparts\n"
                    "  gendef MYDLL.DLL     Produces MYDLL.def\n"
                    "  gendef - MYDLL.DLL   Prints the exports to stdout\n");
-  fprintf (stderr, "\nBuilt on %s\n", __DATE__);
   fprintf (stderr, "\nReport bugs to <mingw-w64-public@lists.sourceforge.net>\n");
   exit (0);
 }
ized Guix</td><td class='sub right'></td></tr></table>
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<div class='path'>path: <a href='/guix/log/?id=c41f88699d8dce182ab422433d9f87cdb83ce2a4'>root</a>/<a href='/guix/log/tests?id=c41f88699d8dce182ab422433d9f87cdb83ce2a4'>tests</a>/<a href='/guix/log/tests/print.scm?id=c41f88699d8dce182ab422433d9f87cdb83ce2a4'>print.scm</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/tests/print.scm?id=c41f88699d8dce182ab422433d9f87cdb83ce2a4&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2019-06-07 22:49:47 +0200'>2019-06-07</span></td><td><a href='/guix/commit/tests/print.scm?id=c0a4db66976dc63decbd612aafb934f44629e321'>import: print: Honor the outputs of inputs (!).</a><span class='msg-avail'>...<span class='msg-tooltip'>Fixes &lt;http://bugs.gnu.org/35893&gt;.
Reported by Jesse Gibbons &lt;jgibbons2357@gmail.com&gt;.

* guix/import/print.scm (package-&gt;code)[package-lists-&gt;code]: Preserve
OUT in the result.
* tests/print.scm (define-with-source): New macro.
(pkg): Use it.
(pkg-source): New variable.
(pkg-with-inputs, pkg-with-inputs-source): New variables.
("simple package"): Refer to 'pkg-source'.
("package with inputs"): New test.
</span></span></td><td>Ludovic Courtès</td></tr>