meson: Fix searching for openssl on MSVC
meson: Fix searching for openssl on MSVC

cc.has_header() is not fatal so we were not actually checking anything

If required: is not specified, dependency() is fatal, which meant that
it was impossible to build without openssl on MSVC.

GNOME/glib-networking,GNOME/glib-networking,GNOME/glib-networking