Use jom to build OpenSSL on Windows

[Nerixyz]

The OpenSSL builds on Windows are really slow because they use nmake which can't parallelize the OpenSSL build (especially when updating the OpenSSL version in CI, this takes quite long). Qt's jom can parallelize the build (see also: openssl/openssl#9931). It can run the Makefile generated by OpenSSL on Windows.

Vcpkg also uses jom to build on Windows

• OpenSSL portfile: https://github.com/microsoft/vcpkg/blob/80d54ff62d528339c626a6fbc3489a7f25956ade/ports/openssl/windows/portfile.cmake#L76
• vcpkg_build_nmake: https://github.com/microsoft/vcpkg/blob/80d54ff62d528339c626a6fbc3489a7f25956ade/scripts/cmake/vcpkg_build_nmake.cmake#L55-L63
• vcpkg_find_acquire_program(JOM): https://github.com/microsoft/vcpkg/blob/80d54ff62d528339c626a6fbc3489a7f25956ade/scripts/cmake/vcpkg_find_acquire_program(JOM).cmake