Make windres output in res format instead of in coff

This makes the output architecture independent, allowing
the x86_64 GNU binutils binary to be used for other
architectures as well, including arm/arm64 which aren't supported
by binutils.

wrappers/windres-wrapper.sh

@@ -0,0 +1,3 @@
+#!/bin/sh
+set -e
+x86_64-w64-mingw32-windresreal "$@" --output-format res