[DEPENDS] Remove the facilities for building win32

Summary:
It is no longer supported, so remove the facilities used to build it and
remove it from the build-all target.
Note: openssl and boost still have configurations for it, I leave them
as they don't hurt and are also still present on core.

Test Plan:

cd depends
make build-all

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D6056