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 9a33f50:debian/patches/reproducible-build.patch

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

This allows gendef and genlib 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);
 }
--- a/mingw-w64-tools/genlib/src/genlib.c
+++ b/mingw-w64-tools/genlib/src/genlib.c
@@ -123,7 +123,6 @@
 "Usage example:\n"
 "  By default, the output file is named after the DLL counterpart\n"
 "  genlib mydef.def    Produces libmydll.a\n"
-"\nBuilt on " __DATE__ "\n"
 "\nReport bugs to <martellmalone@gmail.com>\n"
 ;

scm?id=d7041a69ed01984bf1109a0027cf9f227f03a081'>tree</a><a href='/guix/commit/gnu/packages/chicken.scm?id=d7041a69ed01984bf1109a0027cf9f227f03a081'>commit</a><a href='/guix/diff/gnu/packages/chicken.scm?id=d7041a69ed01984bf1109a0027cf9f227f03a081'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/gnu/packages/chicken.scm'>
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<tr><td><span title='2020-03-03 11:43:05 +0200'>2020-03-03</span></td><td><a href='/guix/commit/gnu/packages/chicken.scm?id=be0c3ac7720ac85667a244bee425a9c6d611de5e'>gnu: chicken: Update to 5.2.0.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/chicken.scm (chicken): Update to 5.2.0.
[home-page]: Use https.

Signed-off-by: Efraim Flashner &lt;efraim@flashner.co.il&gt;
</span></span></td><td>Evan Hanson</td></tr>
<tr><td><span title='2020-02-09 21:00:37 +0100'>2020-02-09</span></td><td><a href='/guix/commit/gnu/packages/chicken.scm?id=7f6cb6bbac181a11859283922037e374a82035db'>gnu: chicken: Update to 5.1.0.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/chicken.scm (chicken): Update to 5.1.0.
[propagated-inputs]: Add gcc-toolchain.

Signed-off-by: Julien Lepiller &lt;julien@lepiller.eu&gt;
</span></span></td><td>Ekaitz Zarraga</td></tr>
<tr><td><span title='2020-02-09 21:00:11 +0100'>2020-02-09</span></td><td><a href='/guix/commit/gnu/packages/chicken.scm?id=2846aec2f7d53b9244ad55c1436437843287426a'>gnu: chicken: Move to a separate module.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/scheme.scm (chicken): Move to chicken.scm.
* gnu/packages/chicken.scm: New file.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add it.

Signed-off-by: Julien Lepiller &lt;julien@lepiller.eu&gt;
</span></span></td><td>Ekaitz Zarraga</td></tr>