Running `OS::AllocatePageSize()` on PPC simulator (which
runs on x64 Linux) will make a `sysconf(_SC_PAGESIZE)` call
which returns the native x64 Linux page size and not the PPC
specific page size.

This can cause a problem if used along side the current value of
`kPageSizeBits` which is set to use PPC value even on Sim.
As an example a newly added DHCECK under https://crrev.com/c/3497363
was failing on PPC Sim as a call to `AllocatableMemoryInDataPage`
was being made which used kPageSizeBits on Sim.

Meanwhile another function was using the `page_size_bits` value which
gets set by _SC_PAGESIZE. The mismatch caused an incorrect final value
being generated which failed the DCHECK.

Change-Id: Iaf2d9cff16bbe5f6be5f3ec6a13b99be94776f48
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3519758Reviewed-by: Junliang Yan <junyan@redhat.com>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Milad Farazmand <mfarazma@redhat.com>
Cr-Commit-Position: refs/heads/main@{#79465}