Fix Windows build errors introduced in D2765

Summary:
See core issue #12386:
https://github.com/bitcoin/bitcoin/issues/12386

Backport of core PR12416

Test Plan:

make check

Build the windows binaries

Reviewers: #bitcoin_abc, deadalnix, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Subscribers: schancel

Differential Revision: https://reviews.bitcoinabc.org/D2779