hurd: Initializy _dl_pagesize early in static builds

We fetch __vm_page_size as the very first RPC that we do, inside
__mach_init (). Propagate that to _dl_pagesize ASAP after that,
before any other initialization.

In dynamic builds, this is already done immediately after
__mach_init (), inside _dl_sysdep_start ().

Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-ID: <20240103171502.1358371-12-bugaevc@gmail.com>