Allow glibc to be compiled without EXEC_PAGESIZE

Allow glibc to be compiled without EXEC_PAGESIZE

We would like to avoid statically defining any specific page size on
aarch64-gnu, and instead make sure that everything uses the dynamic
page size, available via vm_page_size and GLRO(dl_pagesize).

There are currently a few places in glibc that require EXEC_PAGESIZE
to be defined. Per Roland's suggestion [0], drop the static
GLRO(dl_pagesize) initializers (for now, only if EXEC_PAGESIZE is not
defined), and don't require EXEC_PAGESIZE definition for libio to
enable mmap usage.

[0]: https://mail.gnu.org/archive/html/bug-hurd/2011-10/msg00035.html

Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-ID: <20240323173301.151066-4-bugaevc@gmail.com>