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/dlltool-temp-prefix.patch

Description: Specify dlltool's temp prefix
Author: Stephen Kitt <steve@sk2.org>

By default dlltool uses its pid for the object files it generates.
Enforcing its temp prefix allows the files it generates to be
reproducible.

--- a/mingw-w64-crt/Makefile.am
+++ b/mingw-w64-crt/Makefile.am
@@ -36,7 +36,7 @@
   DTDEF32=$(GENLIB) $(DLLTOOLFLAGS32) $(AM_DLLTOOLFLAGS)
   DTDEF64=$(GENLIB) $(DLLTOOLFLAGS64) $(AM_DLLTOOLFLAGS)
 else
-  AM_DLLTOOLFLAGS=-k --as=$(AS) --output-lib $@
+  AM_DLLTOOLFLAGS=-k --as=$(AS) --output-lib $@ --temp-prefix $$(basename $@ .a)
   DLLTOOLFLAGSARM32=-m arm
   DLLTOOLFLAGSARM64=-m arm64
   DLLTOOLFLAGS32=--as-flags=--32 -m i386
ht'></td></tr></table>
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<div class='path'>path: <a href='/guix/log/?id=8c801194b548d1f2d6f47dfcdd5611ae72e29759'>root</a>/<a href='/guix/log/nix?id=8c801194b548d1f2d6f47dfcdd5611ae72e29759'>nix</a>/<a href='/guix/log/nix/libstore?id=8c801194b548d1f2d6f47dfcdd5611ae72e29759'>libstore</a>/<a href='/guix/log/nix/libstore/misc.cc?id=8c801194b548d1f2d6f47dfcdd5611ae72e29759'>misc.cc</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/nix/libstore/misc.cc?id=8c801194b548d1f2d6f47dfcdd5611ae72e29759&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2018-03-30 23:42:07 +0200'>2018-03-30</span></td><td><a href='/guix/commit/nix/libstore/misc.cc?id=c7589cce8d3f9fcb7769e424f341dba8fb3545d0'>daemon: Remove dead code.</a><span class='msg-avail'>...<span class='msg-tooltip'>* nix/libstore/globals.cc (Settings::loadConfFile, Settings::unpack):
Remove.
* nix/libstore/globals.hh: Adjust accordingly.
* nix/libstore/misc.cc (queryMissing): Remove.
* nix/libstore/misc.hh: Adjust accordingly.
* nix/libstore/store-api.cc (followLinksToStore)
(followLinksToStorePath, computeStorePathForHash): Remove.
* nix/libstore/store-api.hh: Adjust accordingly.
</span></span></td><td>Ludovic Courtès</td></tr>