Fix the windows build
Summary: It's been broken for some time.
Test Plan:
mkdir buildwin64 cd buildwin64 make -C ../depends/ HOST=x86_64-w64-mingw32 CONFIG_SITE=$PWD/../depends/x86_64-w64-mingw32/share/config.site ../configure --enable-reduce-exports --disable-bench --disable-gui-tests --without-seeder make dist make
Reviewers: freetrader, schancel, #bitcoin_abc
Reviewed By: schancel, #bitcoin_abc
Differential Revision: https://reviews.bitcoinabc.org/D771